Thiruvenkatarajan et al-2015-anaesthesia

Review Article

Cranial nerve injuries with supraglottic airway devices: a

systematic review of published case reports and series

V. Thiruvenkatarajan,1,2 R. M. Van Wijk3,4 and A. Rajbhoj1,2

1 Staff Specialist Anaesthetist, 3 Head, Department of Anaesthesia, The Queen Elizabeth Hospital, Woodville, SouthAustralia, Australia2 Clinical Senior Lecturer, 4 Associate Professor, Discipline of Acute Care Medicine, The University of Adelaide, Adelaide,South Australia, Australia

SummaryCranial nerve injuries are unusual complications of supraglottic airway use. Branches of the trigeminal, glossopharyn-

geal, vagus and the hypoglossal nerve may all be injured. We performed a systematic review of published case reports

and case series of cranial nerve injury from the use of supraglottic airway devices. Lingual nerve injury was the most

commonly reported (22 patients), followed by recurrent laryngeal (17 patients), hypoglossal (11 patients), glossopha-

ryngeal (three patients), inferior alveolar (two patients) and infra-orbital (one patient). Injury is generally thought to

result from pressure neuropraxia. Contributing factors may include: an inappropriate size or misplacement of the

device; patient position; overinflation of the device cuff; and poor technique. Injuries other than to the recurrent lar-

yngeal nerve are usually mild and self-limiting. Understanding the diverse presentation of cranial nerve injuries helps

to distinguish them from other complications and assists in their management..................................................................................................................................................................

Correspondence to: V. Thiruvenkatarajan

Email: [email protected]

Accepted: 22 September 2014

Presented at the Australian and New Zealand College of Anaesthetists’ Annual Scientific Meeting, Singapore, May

2014.

IntroductionThe classic laryngeal mask airway (cLMA, LMA North

America, San Diego, CA, USA) was invented by Dr

Archie Brain in 1981 and introduced into clinical prac-

tice in 1988 [1, 2]. Since that time, other airway

devices that do not pass through the larynx have been

invented, and these and the original LMA are referred

to as supraglottic airway devices. They are widely used

in day-to-day practice, being used in roughly 50% of

all general anaesthetic procedures [2].

The morbidity associated with the use of supra-

glottic airway devices is largely defined by minor phar-

yngolaryngeal complications such as: sore throat (17–

42% of patients) [3]; soft tissue abrasion (16–32%) [4];

hoarseness and dysphagia. Cranial nerve injury after

the use of a supraglottic airway device is an unusual

but more serious complication. So far, injuries of lin-

gual, inferior alveolar, infra-orbital, glossopharyngeal,

recurrent laryngeal and hypoglossal nerves have been

reported. The true incidence of these injuries is not

known; we suspect many are not reported. We have

conducted a systematic review of all published case

reports and case series of cranial nerve injury following

the use of supraglottic airway devices. The aim of this

review is to analyse and summarise the features of cra-

nial nerve injuries associated with supraglottic airway

344 © 2014 The Association of Anaesthetists of Great Britain and Ireland

Anaesthesia 2015, 70, 344–359 doi:10.1111/anae.12917

devices, with particular emphasis on contributing

factors.

MethodsWe searched PubMed and Embase for material pub-

lished up to April 31, 2014, and identified case reports

and case series mentioning cranial nerve injuries associ-

ated with supraglottic airway devices (details of the

search strategy are presented in the Appendix). The

search was not limited to a particular start date and we

did not impose a restriction on language of publication.

The bibliographies of the identified publications were

hand-searched for additional reports. We included

reports of both adults and children, as there seems to be

no clear evidence that the mechanisms of nerve injury

differ between these two groups. To be included, the

reports had to describe and confirm the clinical evidence

of cranial nerve injury in association with the use of any

type of supraglottic airway device. Two authors working

independently extracted the following data: age, sex and

weight of the patient; size and type of device inserted;

use of nitrous oxide; cuff volume and pressure; times of

onset and resolution of symptoms; management; and

any contributing factors.

ResultsOur searches generated a total of 164 articles from

PubMed and 191 from Embase. After excluding 45

duplicates, 312 reports were left. Of these, there were

53 reports meeting the eligibility criteria (Fig. 1),

reporting a total of 56 patients. The reports were pub-

lished between 1994 and 2014; our analysis of four

reports was restricted to the abstract as we were unable

to secure translations. Patient ages ranged from

9 months to 75 years.

Recurrent laryngeal nerve damageOur review identified 16 cases of recurrent laryngeal

nerve injury [5–19]. Of these, 13 were reported with

the cLMA and its variants [5–16], two with the Pro-

Seal LMATM [17, 18] and one with the Air-QTM LMA

[19] (Table 1).

Of all the cranial nerve injuries, damage to the

recurrent laryngeal nerve was most likely to present

with significant morbidity. Uniquely among the nerve

injuries described in this review, it may present both

intraoperatively and postoperatively. The recurrent lar-

yngeal nerve ascends in the tracheo-oesophageal

groove and enters the larynx by passing under the

lower border of the inferior constrictor muscle at the

apex of the piriform fossa [5]. When correctly placed,

the tip of the LMA cuff is positioned at the inferior

border of the hypopharynx, against the upper oesopha-

geal sphincter at the level of the C6–C7 vertebral inter-

space (Fig. 2). The nerve is vulnerable to injury as it

enters the larynx, where it can be pinched against the

cricoid cartilage (Figs. 2 and 3). Unilateral paralysis

results in the vocal cord’s resting in the paramedian

position. In this situation, the laryngeal inlet will be

adequate and airway obstruction is unlikely. However,

inadequate glottic closure might result in hoarseness,

and laryngeal incompetence may lead to impaired

coughing and risk of aspiration. Bilateral palsy may

cause the vocal cords to be positioned in the midline,

with narrowing of the glottic aperture. This may pres-

ent as dyspnoea or inspiratory stridor, and occasionally

severe respiratory distress [20]. Respiratory difficulty,

requiring intubation or tracheostomy, and permanent

voice impairment are the most severe complications.

In the cases reported, it was sometimes difficult to

establish the diagnosis. For instance, the authors of

one report could not ascertain whether the vocal cord

palsy (presenting as voice impairment) after LMA use

was due to the device, or to the presence of a cervical

spine osteophyte compressing the nerve close to the

trachea and oesophagus [21]. Furthermore, vocal cord

palsy after the use of supraglottic airway devices clo-

sely resembles arytenoid cartilage subluxation and is

thus likely to be under-diagnosed [22, 23].

In the 16 cases we reviewed, the time of presenta-

tion varied from immediately after the insertion of the

LMA to up to 48 h later. Hoarseness was the most

common manifestation, followed by dysphagia and

dysphonia. Four reports documented bilateral injury.

Two patients required tracheostomy [9, 17]; one pre-

sented intra-operatively, the other 2 h after removal

[9]. A child required mechanical ventilation [12]. The

fourth patient developed features of unilateral paralysis

(aphonia and difficulty in coughing) but was found to

have bilateral paralysis when inspected through the fi-

breoptic bronchoscope [16]. Both the patients in

whom the Pro-Seal was used also needed tracheosto-

© 2014 The Association of Anaesthetists of Great Britain and Ireland 345

Thiruvenkatarajan et al. | Cranial nerve injuries with supraglottic airway devices Anaesthesia 2015, 70, 344–359

mies; one was performed in the operating room at the

time of the injury; the other required the procedure

two weeks after the anaesthetic, following aspiration

pneumonia. Co-existing disorders in the form of spi-

nocerebellar ataxia [17] and CREST (calcinosis, Ray-

naud’s phenomenon, oesophageal dysmotility,

sclerodactyly and telangiectasia) with Sjogren’s syn-

drome [18] were present in these patients. Flexible fi-

breoptic bronchoscopy or nasal endoscopy may help

in the immediate diagnosis of the more serious bilat-

eral presentations and assist in identifying conditions

that might require urgent treatment such as mucosal

trauma and arytenoid dislocation. Electromyography,

CT scan, MRI scan or video stroboscopy may also help

in distinguishing arytenoid dislocation [24] and other

causes of cord palsy. Of the 16 patients, five were

managed conservatively with recovery times varying

from 1 h up to 19 months. Partial recovery was noted

in four patients. Laryngoplasty, thyroplasty and

mechanical ventilation were required in three separate

patients [6, 7, 12]. Persisting voice damage with partial

recovery of vocal cord function was noted in five

patients [6, 7, 13, 14, 17].

Cuff pressure was described in only one patient

[17]. Cuff volume was mentioned in nine patients and

all except one [13] had an appropriate volume. Cuff

overinflation was postulated in two reports [13, 18].

Other contributory factors suggested were: incorrect

size of device for the patient [6, 8, 13]; the use of lido-

caine jelly [13, 16]; long duration of surgery [9]; poor

insertion technique [22]; reduced mucosal circulation

[17, 18] and activation of the inflammatory cascade

[14, 17] (Table 4).

Hoarseness after supraglottic airway use cannot

always be attributed to transient laryngeal irritation [6];

the possibility of recurrent laryngeal nerve injury should

always be considered. Persistent cough, speech impair-

ment or respiratory compromise warrant careful

examination and follow-up with referral to an otolaryn-

gologist [7]. Management options other than conserva-

tive treatment include voice therapy, glucocorticoids

and surgical interventions for persisting palsies. Finally,

though supraglottic airway may be preferable to tracheal

intubation in professional voice users, such patients

should be informed pre-operatively about this recurrent

laryngeal nerve injury and its consequences [5].

Records identified through manual search (n = 3)

Duplicates removed (n = 45)

Relevant articles screened

(n = 313)

Excluded: Based on title and abstract (n = 222)

Full text articles assessed for eligibility (n = 91)

Excluded (n = 38)Not meeting theInclusion criteria (n = 37)Unable to get Japanese abstract (n = 1)Reports included (n = 53)

(Includes abstract only data from 3 Japanese and one Danish report)

Trigeminal nerve Reports (n = 23)Patients (n = 25)Lingual (n = 22)Inferior alveolar (n = 2)Infra-orbital (n = 1)

Recurrent laryngeal nerveReports (n = 16)Patien ts (n = 17)

Hypoglossal nerveReports and patients (n = 11)

Glossopharyngeal nervePatients (n = 3)

Iden

tific

atio

n S

cree

ning

Elig

ibilit

yIn

clud

ed

Number of records identified from PubMed and Embase(n = 355)

Figure 1 Flow diagram of the literature search and selection process.


Anaesthesia 2015, 70, 344–359 Thiruvenkatarajan et al. | Cranial nerve injuries with supraglottic airway devices

Table

1Summaryof

recurrentlaryngealnerveinjuries

followinguseof

differenttypesof

supraglottic

airw

aydevice.

Reference

Age;

years/

sex

Weight;

kg

Sizeof

device

Duration

of

surgery;

min

N2O

use

Cuff

pressure/

volume

measu

red

Laterality

Symptoms/

signs

Tim

eof

onset

Management

Tim

eto

reco

very

Contributing

factors

Classic

LMA

Wadelek

etal.[8]

57/M

98

470

No

33ml

Unilateral

Hoarseness

dysphagia,

tongue

deviation

PACU

MRI

Few

months

Toosm

all

amask?,

Semi-supine

position

Endo

etal.[9]

63/F

48

3425

Yes

20ml

Bilateral

Shortness

ofbreath

2h

Trach

eostomy

1month

Longduration,

arytenoid

compression

Chanand

Grillone[6]

50/M

120

560

NR

NR

Unilateral

Hoarseness,

dysphonia

PACU

CTscan,

Injection

laryngoplasty

19months

(partial)

Toolargea

mask?

Bruce

etal.[10]

21/M

NR

575

Yes

NR

Unilateral

Hoarseness

2days

Conservative

5months

NR

Minoda

etal.(A

)[11]

58/F

NR

NR

NR

NR

NR

Unilateral

Hoarseness,

dysphagia

NR

NR

2months

NR

Sacks

etal.[12]

4/M

17

290

Yes

7ml

Bilateral

Inspiratory

stridor

Endofcase

Intubation,

ventilation

24h

Intra-operative

cuff

pressure

increase

Lowinger

etal.[7]

44/M

NR

450

Yes

20ml

Unilateral

Dysphonia,

aphonia

24h

Thyroplasty

18months

(partial)

NR

Brimaco

mbe

etal.[13]

74/M

83

360

Yes

35ml

Unilateral

Hoarseness,

sore

throat

Few

hours

Conservative

3months

(partial)

Poortech

nique,

toosm

alla

mask,

ove

r-inflation

ofcu

ff,

lidocainejelly

Cros

etal.[14]

19/M

67

490

Yes

20ml

Unilateral

Dysphonia,

laryngeal

inco

mpetence,

fluid

aspiration,

sore

throat

Few

hours

NR

2months

Isch

aemic

inflammatory

reaction

Cros

etal.[14]

54/M

52

360

Yes

30ml

Unilateral

Dysphagia,

hoarseness,

laryngeal

inco

mpetence

Few

hours

NR

6months

(partial)

Ove

r-inflation

ofcu

ff

Daya

etal.[5]

64/F

36

460

Yes

NR

Unilateral

Hoarseness

48h

Conservative

3months

Pressure

neuropraxia



Table

1(continu

ed)

Reference

Age;

years/

sex

Weight;

kg

Sizeof

device

Duration

of

surgery;

min

N2O

use

Cuff

pressure/

volume

measu

red

Laterality

Symptoms/

signs

Tim

eof

onset

Management

Tim

eto

reco

very

Contributing

factors

Lloyd

Jones

and

Hegab[15]

39/F

72

430

Yes

30ml

Unilateral

Hoarseness

2days

NR

3weeks

Pressure

neuropraxia

Inomata

etal.[16]

45/F

41

397

Yes

15ml

Bilateral

Aphonia

Immediate

Conservative

40min

Lidocainejelly

Pro-Seal

Carron

etal.[17]

67/F

60

460

No

60cm

H2O

Bilateral

Laryngeal

oedema

Intra-

operative

Trach

eostomy

NR

Reduced

muco

salblood

flow,altered

cricoarytenoid

function,

inflammatory

cascade

Kawauch

ietal.[18]

71/F

50

3117

Yes

40ml

Unilateral

Dysphagia,

hoarseness,

coughing

24h

Minitrach

eostomy

2months

(partial)

Double

the

reco

mmended

volume,

reduced

muco

salblood

flow

Air-Q

TMLM

ABlais

etal.[19]

75/F

NR

3NR

No

NR

Unilateral

Vocalco

rdbowing

toright

After

insertion

LMA

adjustment

Immediate

Mech

anical

force

PACU,po

st-anaesthesia

recovery

unit;MRI,magneticresonanceim

aging;

NR,no

trecorded;A,abstract

data.



Trigeminal nerve injuryThe three divisions of this nerve are the ophthalmic,

maxillary and mandibular. Of all the branches of the

trigeminal nerve, the lingual nerve, a peripheral branch

of the mandibular nerve, was the most commonly

injured by supraglottic airway use. The inferior alveo-

lar branch of the mandibular nerve can also be dam-

aged. The only branch of the maxillary nerve at risk is

the infra-orbital nerve [25]. We identified 25 cases of

nerve injuries related to the peripheral branches of the

trigeminal nerve (Table 2). Of these, 22 were lingual

nerve injuries [24, 26–44], two inferior alveolar [45,

46] and one infra-orbital [25].

Of the 22 lingual nerve injuries, 14 were associated

with the use of the cLMA and its variants [24, 26–37].

The Pro-Seal, LMA SupremeTM, i-gel� and COPATM

(cuffed oropharyngeal airway) had two associated inju-

ries each [38–44].

The lingual nerve lies immediately beneath the

mucosa on the inner surface of the mandible just

below the roots of the third molar tooth [37]. It then

passes forward to the side of the tongue, crossing the

hyoglossus muscle, and divides into terminal branches

that lie directly under the mucosa of the tongue. The

nerve is susceptible to injury by compression or

stretching by supraglottic airway devices at two points:

the lateral edge of the tongue base; and the medial

aspect of the inner surface of the mandible close to the

third molar [47, 48] (Figs. 2 and 4). Transient numb-

ness of the anterior tongue and altered taste perception

(dysgeusia) were the most common presentations.

Numbness at the tip and the lateral half of the tongue

can also be present, and can affect speech articulation

[49]. Symptoms can occur as early as a few minutes

after insertion to as late as 24 h. Lingual nerve injury

has to be differentiated from hypoglossal nerve dam-

age, which presents predominantly as motor weakness

of the tongue. No specialised investigations are

required but a subjective sensory assessment of the

tongue is useful, and aids in the monitoring of recov-

ery [48].

The cuff pressure was described in only three

patients [24, 25, 29]; the cuff volume was recorded in 11

patients. The contributing factors discussed included:

nitrous oxide use; malpositioning; incorrect sizing; pro-

longed duration of surgery; and chemical neuronitis

secondary to the use of wrong lubricant (Table 4).

Recovery occurred in all patients with lingual

nerve injury without specific treatment; this took from

a few hours to up to six months. Similar self-limiting

symptoms are frequently encountered after dental

Infra-orbital nerve

Lingual nerveInferior alveolarnerve

Hypoglossalnerve

Recurrent laryngealnerve

Hyoid bone

Mental nerve

C6

Figure 2 Schematic illustration of the position of a su-praglottic device in relation to the cranial nerves ofinterest.

Figure 3 Anatomical preparation of a laryngeal maskairway in situ. The cuff is inflated next to the pointwhere the thyroid and cricoid cartilages meet (arrow)where the recurrent laryngeal nerve is situated. At thislocation, the nerve enters the larynx from within thetracheo-oesophageal groove. ‘Oesoph’ denotes oesopha-gus (reproduced with permission from [21]).



Table

2Summaryof

trigem

inal

nerveinjuries

followinguseof

differenttypesof

supraglottic

airw

aydevices.

Reference

Age;

years/

sex

Weight;

kg

Size

Duration

of

surgery;

min

N2O

use

Cuff

pressure/

volume

measu

red

Laterality

Symptoms/

signs

Tim

eof

onset

Management

Tim

eto

reco

very

Contributing

factors

Lingualnerve

Classic

LMA

variants

Dhillonand

O’Leary

[24]

52/F

NR

460

No

<60cm

H2O

Bilateral

Numbness,

taste

disturbance

Instant

Conservative

4weeks

EBUS

induced

LMA

move

ment

ElToukhyand

Tweedie

[26]

36/F

NR

4180

No

No

Bilateral

Numbness,

taste

disturbance

PACU

Conservative

6weeks

NR

Foleyetal.[27]

21/M

79

545

No

40ml

Unilateral

Numbness,

taste

disturbance,

Few

hours

Conservative

4weeks

NR

Foleyetal.[27]

50/F

101

370

Yes

NR

Unilateral

Numbness

PACU

Conservative

4weeks

NR

In� acioetal.[28]

55/F

75

4150

NR

20ml

Bilateral

Numbness,

taste

disturbance

1h

Conservative

2weeks

Smallsize

Fidelerand

Schroeder[29]

32/F

NR

460

NR

50cm

H2O

Unilateral

Numbness,

taste

disturbance

Few

hours

Conservative

4days

TMJ

subluxa

tion

Cardoso

etal.[30]

36/F

60

3120

NR

30ml

Bilateral

Numbness,

taste

disturbance

1h

Conservative

3weeks

Smallsize

Arimune(A

)[31]

27/M

NR

NR

NR

NR

NR

Unilateral

Taste

disturbance

NA

NR

NA

NR

Koya

ma

etal.(A

)[32]

20/M

NR

NR

NR

Yes

NR

NR

Tasteloss

24h

NR

6months

Malposition

Gaylard

[33]

40/M

NR

460

Yes

20ml

Unilateral

Numbness,

taste

disturbance

24h

Conservative

2months

NR

Majumderand

Hopkins[34]

27/F

NR

320

Yes

20ml

Bilateral

Numbness,

taste

disturbance

PACU

Conservative

6weeks

Nerve

compression

Ostergaard

etal.(A

)[35]

73/M

NR

NR

140

Yes

NR

NR

Taste

disturbance

1week

NR

6months?

partial

NR

Ahmedand

Yentis[36]

26/M

NR

430

Yes

30ml

Unilateral

Numbness,

taste

disturbance

PACU

NR

NR

NR

Laxton[37]

42/F

54

335

Yes

20ml

Unilateral

Numbness,

taste

disturbance

Few

hours

Conservative

4months

(90%

reco

very)

Multiple

factors



Table

2(continu

ed)

Reference

Age;

years/

sex

Weight;

kg

Size

Duration

of

surgery;

min

N2O

use

Cuff

pressure/

volume

measu

red

Laterality

Symptoms/

signs

Tim

eof

onset

Management

Tim

eto

reco

very

Contributing

factors

Pro-Seal

Brimaco

mbe

etal.[38]

61/M

74

5150

Yes

20ml

Unilateral

Numbness,

taste

disturbance

Immediate

Conservative

15days

Non-supine,

shoulder

surgery,

N2O,long

duration

Brimaco

mbe

andKeller[39]

64/F

76

445

No

2ml

Unilateral

Numbness

2h

Conservative

10h

Big

size

SupremeLM

AThiruve

nkatarajan

etal.[40]

45/F

61

3105

No

No

Tonguetip

Numbness

PACU

Conservative

3weeks

Smallsize

,cu

ffpressure

not

monitored

Rujirojindakul

etal.[41]

43/F

65

475

No

No

Tonguetip

Numbness

24h

Conservative

2weeks

Excess

cuff

pressure

i-gel

Renesetal.[42]

69/M

78

445

NR

NR

Bilateral

Numbness,

taste

disturbance

Few

hours

Conservative

8weeks

i-geldesign

Rujirojindakul

etal.[41]

33/F

53

345

No

NR

Tonguetip

Numbness

24h

Conservative

2weeks

NR

COPA

Kadry

and

Popat[43]

29/F

60

10

65

Yes

40ml

Unilateral

Numbness,

taste

disturbance

PACU

Conservative

10days

Multiple

factors

Laffon

etal.[44]

32/F

65

920

Yes

38ml

Bilateral

Numbness

PACU

Conservative

2h

Cuff

ove

rinflation

Inferior

alveolarnerve

Classic

LMA

variants

Hanumanthiah

etal.[45]

35/M

85

4120

Yes

30ml

Unilateral

Lowerlip

numbness

PACU

Conservative

2weeks

Vascular

compression

i-gel

Theronand

Loyd

en[46]

NR/F

NR

460

NR

NR

NR

Lowerlip

numbness

andulcer

NR

Conservative

4days

(partial)

i-geldesign



procedures [27]. However, although lingual nerve

damage does not lead to severe morbidity, disturbances

in taste, speech and the tongue trauma can cause sig-

nificant discomfort until recovery occurs.

The inferior alveolar nerve lies superficially between

the third molar tooth and the ramus of the mandible,

where it is vulnerable to injury [45] (Fig. 2). Injury pre-

sents as sensory loss of the lower lip resulting from

neuropraxia of the terminal branch (the mental nerve);

this creates the potential for subsequent lip trauma.

Both reported cases (cLMA and i-gel) recovered within

a week. The wide buccal stabiliser and the integral bite

block design of the i-gel makes it bulkier and harder

around the lips compared with other devices. This

could obscure the anaesthetist’s view of the lower lip

looking from the head end of the patient; accidental

taping of the lower lip to the lower bite block of the

i-gel might also contribute to nerve injury [46].

The only reported case of infra-orbital nerve injury

occurred with the LMA Supreme [25]. The maxillary

nerve continues as the infra-orbital nerve and inner-

vates the lower eyelid, upper lip, cheek and side of the

nose (Fig. 2). Injury to the infra-orbital nerve presents

as swelling and sensory loss of the upper lip. In the

report, the fixation tab of the device was fixed in close

contact with the upper lip [25]. The fixation tab is a

new feature, absent from other models of supraglottic

airway devices; it is a rectangular structure projecting

over the upper lip facilitating insertion and fixation.

According to the instructions from the manufacturer,

the distance between the fixation tab and upper lipTable

2(continu

ed)

Reference

Age;

years/

sex

Weight;

kg

Size

Duration

of

surgery;

min

N2O

use

Cuff

pressure/

volume

measu

red

Laterality

Symptoms/

signs

Tim

eof

onset

Management

Tim

eto

reco

very

Contributing

factors

infra-orbitalnerve

SupremeLM

ACarron

etal.[25]

64/F

68

480

No

60cm

H2O

NR

Numbness,

swelling,

(midline

upperlip)

PACU

Conservative

14days

Reduced

fixa

tion

tabto

lip

distance

COPA,cuffed

orop

haryngealairw

ay;NR,no

trecorded;PACU;po

st-anaesthesia

care

unit;A,abstract

data;EBUS,

endo

bron

chialultrasou

nd;TMJ,Tem

poromandibu

lar

joint.

Third molar

Lingual plate

Lingual nerve

Figure 4 Illustration of the lingual nerve entering themouth at the level of the 3rd molar tooth on the lin-gual side of the mandible, where it is close to the peri-osteum and prone to compression.



should be between 0.5 and 2 cm [50]. If the fixation

tab is found to press against the upper lip, a larger size

is warranted. The authors felt that this injury could

have been avoided by following the manufacturer’s

instructions. However, it may be difficult to maintain

this distance intra-operatively as the tape or tie secur-

ing the device is passed across the fixation tab, making

it difficult to inspect the distance. In addition, changes

in cuff pressure during anaesthesia may alter this dis-

tance [25].

Hypoglossal nerve injuryOur review identified 11 cases of hypoglossal nerve

injury [29, 51–60]. Of these, nine were after the cLMA

and two with the Pro-Seal (Table 3). Nine were isolated

injuries, the other two were bilateral. Eight cases were

reported in adults, two in adolescents and one in an

infant. Nitrous oxide was used in five patients and the

data were missing in three reports.

The hypoglossal nerve lies above the greater horn

of the hyoid bone at the angle of mandible before

turning forwards and medially towards the tongue

[51]. The nerve is vulnerable to neuropraxia from

compression injury due to an overinflated or malposi-

tioned cuff at the level of the greater horn of the hyoid

bone [61] (Fig. 2).

The nerve supplies the ipsilateral intrinsic and

extrinsic muscles of the tongue apart from the palato-

glossus [52, 62]. Ipsilateral injury presents as tongue

deviation to the affected side together with unilateral

muscle weakness [53, 63]. Bilateral injury manifests as

fasciculations, motor weakness of the tongue, dysar-

thria and dysphagia [54]. The onset time varied from

soon after awakening to as late as first postoperative

day. However, diagnosis can be confused by the co-

existence of other cranial nerve injuries. A review of

hypoglossal nerve injury after tracheal intubation

revealed that a quarter of the patients also had ipsilat-

eral lingual nerve damage [62]. These two nerves lie

closely together at the lateral margin of the tongue

where they can be compressed [62]. One of the two

reports with a Pro-Seal also had features of lingual

nerve injury [60]. As opposed to lingual nerve injury,

where both the cuff and the shaft of the supraglottic

airway can create pressure points, hypoglossal nerve

stretching is only related to the cuff of the device.

Internal carotid artery dissection and central venous

catheterisation through the internal jugular vein are

other rare causes of hypoglossal nerve injury [62].

Patients with severe or bilateral symptoms should

be referred to a neurologist for further management

(peripheral vs central tongue palsy). Extracranial

Doppler, duplex sonography or MRI may be required

to differentiate device-induced injury from internal

carotid artery dissection [62]. Spontaneous recovery is

possible with conservative rehabilitative measures such

as diet modifications, steroids and speech therapy [62].

All the reported patients recovered completely within a

few days to months, except one case where residual

motor weakness of the tongue persisted [57].

Cuff pressure was recorded in only one case

whereas the volume was mentioned in seven cases. In

two cases, an incorrect size was thought to contribute

to the injury [51, 58, 61].

Other contributory factors outlined from the

reports were: use of nitrous oxide; presence of a hypo-

pharyngeal haematoma in an anticoagulated patient;

extreme head rotation along with prolonged duration;

coexistent rheumatoid arthritis; and cuff overinflation

and malposition (Tables 3 and 4).

Multiple cranial nerve injuriesThere were two cases of combined lingual and glosso-

pharyngeal nerve injuries [31, 44] and one report of a

combination of lingual, glossopharyngeal and hypo-

glossal nerve injuries [29]. Glossopharyngeal nerve

injury presents as taste and sensory disturbance to the

posterior third of the tongue, loss of the pharyngeal

reflex, dysphagia, and deviation of the uvula to the

opposite side [47]. Temporomandibular joint subluxa-

tion was thought to account for the combination of

these three nerve injuries [29].

There was one case of Tapia’s syndrome, which is a

combined extracranial ipsilateral injury of the recurrent

laryngeal and hypoglossal nerves [8]. Pressure neuropr-

axia of both nerves due to an overinflated cuff and

stretching are the proposed mechanisms. The hypoglos-

sal nerve is situated on the most lateral prominence of

the transverse process of the first cervical vertebra and

crosses the vagus nerve [8]; the nerves are likely to be

stretched over this prominence. The patient described

also had features of lingual nerve injury [8].



Table

3Summaryof

hypo

glossalnerveinjuries

followinguseof

differenttypesof

supraglottic

airw

aydevices.

Reference

Age;

years/

sex

Weight;

kg

Size

Duration

ofsurgery;

min

N2O

Use

Cuff

pressure/

volume

measured

Laterality

Symptoms/

signs

Tim

eof

onset

Management

Tim

eto

reco

very

Contributing

factors

Classic

LMA

variants

Trujilloetal.[55]

9M/M

9.7

1.5

45

No

NR

Unilateral

Tongue

deviation

2h

Conservative

,speech

therapy

3weeks

NR

Fidelerand

Schroeder[29]

32/F

NR

460

NR

50cm

H2O

Unilateral

Tongue

deviation

Few

hours

Conservative

4days

TMJ

subluxa

tion

hyp

othesised

Lo[51]

48/M

NR

3120

NR

20ml

Unilateral

Tongue

deviation,

dysphagia

3h

Conservative

2weeks

NR

Rodriguezetal.[53]

15/M

NR

4NR

NR

NR

Unilateral

Dysarthria,

tongue

deviation

2h

Steroids

MRI

15days

NR

Sommeretal.[52]

15/M

88

490

No

20ml

Bilateral

Dysphagia,

dysarthria,

tongue

fasciculations

&motor

weakness

Immed-

iate

Steroids

MRI

4weeks

Extremehead

rotation,

prolonged

surgery

Stewart

and

Lindsay[54]

54/M

83

545min

Yes

40ml

Bilateral

Dysphagia,

dysarthria,

tongue

weakness,

7kgweight

loss

Immed-

iate

CNSco

nsult

Speech

therapy

6weeks

Cuff

ove

rinflation,

malposition

Umapathyetal.[56]

46/M

NR

4NR

No

NR

Unilateral

Tongue

deviation,

dysphagia

6h

Conservative

6weeks

NR

KingandStreet[57]

55/M

NR

4NR

Yes

25ml

Unilateral

Dysphagia,

dysarthria

4h

Conservative

8days

Antico

agulation

Nagaietal.[58]

62/F

36

33h

Yes

20ml

Unilateral

Dysphagia,

tongue

deviation

3h

Vitamin

B12,

steroids

1week

NR

Pro-Seal

Trive

di[59]

24/M

62

4300

Yes

30ml

Unilateral

Dysphagia,

dysarthria

1h

Steroids,

vitamin

B12

6weeks

Non-neutral

headposition,

N2O,

prolonged

duration

Tr€ umpelm

annand

Cook[60]

28/F

NR

5210

Yes

40ml

Unilateral

Dysphagia,

tongue

numbness

1day

Conservative

4months

N2O,prolonged

surgery

NR,no

trecorded;TMJ,tempo

romandibu

larjoint;MRI,magneticresonanceim

aging;

CNS,

centralnervou

ssystem

.



DiscussionInjuries to cranial nerves from supraglottic airway

devices present in different ways. In the reports we

retrieved, symptoms were minimal with trigeminal and

hypoglossal nerve neuropraxia, and the outcome was

good. Conversely, most patients with recurrent laryn-

geal injury presented with significant dysfunction.

Injuries can be complex in that, while many causative

mechanisms have been proposed, many happened

apparently for no identifiable reason. Awareness of

these injuries and their presentation is crucial in subse-

quent management. In the postoperative setting, anal-

gesics and residual anaesthetic drugs might mask

symptoms and signs, leading anaesthetists to overlook

the problem.

Although information on contributing factors and/

or the mechanism of injury was missing in over half the

reports included, two factors are worthy of mention.

The first is intracuff pressure. Even at recommended

cuff volumes, intracuff pressure can exceed the recom-

mended values [64] and potentially exceed the critical

capillary perfusion pressure of the pharyngeal mucosa

[65, 66]. Nitrous oxide diffusion into the cuff can

increase the cuff volume up to 38% within 30 min and

up to 50% before the end of anaesthesia [67]. Further-

more, if the cuff is inflated to the maximal recom-

mended volume, the cuff pressure can double within

60 min [68]. The cuff pressure varies between individ-

ual patients for a given volume of air [1]. A recent study

shows that, even in the absence of nitrous oxide, the

cuff pressure of the LMA can exceed the recommended

level in about three quarters of the patients; cuff pres-

sure was frequently over 120 cmH2O [69]. Measuring

the cuff pressure, and keeping it below 60 cmH2O, has

been shown to reduce pharyngolaryngeal complications

by 70% [3]. However, apart from the manufacturers’

recommendation of a maximum cuff pressure of

60 cmH2O, there are no clinical guidelines endorsing

this particular value, so others may be better.

Second, the case reports suggest that components

other than the cuff can also cause nerve injury. These

include the shaft of the device compressing the lingual

nerve at the periosteum close to the third molar, and

the fixation tab of the LMA Supreme causing infra-

orbital nerve damage. It is interesting to speculate

whether differences in device design might influence

their propensity to cause nerve injury – do the wider

shaft and the more rigid material of the LMA Supreme

make it more likely to damage the lingual nerve injury

compared with the cLMA, for instance? Current

knowledge suggests that directly measured pressures

exerted on the oropharyngeal mucosa were very low

and similar among cLMA, LMA Supreme and i-gel

[70, 71], so one might assume that they have a compa-

rable safety profile in this respect.

As many anaesthetists are more aware of periph-

eral nerve damage during anaesthesia and surgery,

some comparative features are relevant.

Most cranial nerve injuries are identified within the

first 24 h after surgery whereas peripheral neuropathies

are usually identified after 48 h [72]. Anaesthetic factors

play a predominant role in the presentation of cranial

nerve injuries, whereas surgical and predisposing factors

have a greater role in causing peripheral nerve injuries

[73]. Most of the cranial nerve injuries (apart from some

recurrent laryngeal nerve injuries) are neuropraxic in

nature. Hypertension, smoking and diabetes are well-

recognised risk factors of peripheral nerve injury [74];

however, data on a similar risk factors for cranial nerve

injury are lacking, though it seems plausible that those

with pre-existing neuropathic disease might be more

vulnerable. Lastly, while electromyography is widely

used in the management of peripheral nerve injury [75],

its utility was not described in the reports of cranial

Table 4 Possible contributing factors to cranial nerveinjuries with supraglottic airway devices.

Anaesthesia-related factorsExcessive cuff inflation, > 60 cm H2OFailure to measure and adjust the cuff pressureInappropriate size selectionPeri-operative manipulation of the deviceNitrous oxide useMalpositioningTraumatic insertionPoor techniqueChemical neuronitis

Patient-related factorsDiabetes mellitusCollagen vascular disordersPeripheral vascular disorders

Surgery-related factorsLateral positionExtreme head rotationProne positionProlonged duration



nerve injury after supraglottic airway use. Nonetheless,

electromyography was employed in the management of

hypoglossal nerve palsy as a complication of tracheal

intubation [76] implying its possible role as a diagnostic

tool in nerve palsy after supraglottic airway use.

If cranial nerve injury is suspected, details of the

timing and progression of the symptoms, with a par-

ticular emphasis on the predisposing factors should be

elicited [75]. Attempts should be made to ascertain the

mechanism of injury and a basic neurological exami-

nation should be undertaken, concentrating on the

sensory and motor deficits. Simple assessments such as

light touch, pinprick and two-point discrimination

should be used to record baseline function and help

monitor progression. Documentation should include

schematic illustration of the areas involved, and the

nature of the injury should be well described. Patients

with minor neuropraxic injuries should be reassured

about recovery and followed up by telephone. Appro-

priate consultations should be organised as early as

possible for complicated presentations, including neu-

ropathic pain.

Although we systematically sought case reports

and series for this review, we did not include data

about cranial nerve injuries that might have appeared

within observational or randomly assigned studies of

supraglottic ariways. We did not contact device manu-

facturers nor national registries of medical device

problems. We are unable to calculate estimates of fre-

quency as the true number of nerve injuries is

unknown and we have no reliable denominator. Fur-

thermore, the evidence for specific causative factors is

moderate at best. Nevertheless, we have compiled the

largest collection of published reports to date and we

are in a position to make two comments for practice.

The first relates to device size. Currently, most

manufacturers recommend weight-based selection of

size of supraglottic airway device. However, Asai and

Brimacombe argue against using a single factor in size

selection, since there is no definite relationship

between gender, weight, height, dimensions of the oro-

pharynx and body mass index [77]. Individual ana-

tomical variations in relation to the shape and size of

the oropharynx are relevant when choosing a size of

LMA. A larger size mask where the cuff is not visible

in the back of the mouth and the cuff volume inflated

to the minimum necessary seems to be an appropriate

technique [77].

The second relates to causation. We suggest that

cranial nerve injuries may not be completely pre-

ventable and should not always be assumed to rep-

resent sub-standard care. Nevertheless, we advocate

the use of a cuff manometer and recommend that

the cuff pressure is maintained below < 60 cm H2O.

A careful, gentle insertion technique; proper fixation;

and early identification and correction of misplace-

ment will also help.

In terms of research, large prospective epidemio-

logical studies are needed to determine the true inci-

dence of these injuries, as well as improving our

understanding of them. A better knowledge of the ana-

tomical configuration of new devices might also con-

tribute to greater safety, and nerve injury should be

incorporated as a secondary adverse outcome in future

studies evaluating supraglottic airway devices. The dif-

ferences between various devices in causing these inju-

ries are also worthy of further investigation.

AcknowledgementsThe authors thank Dr Michael Draper, research librar-

ian at Barr Smith Library, University of Adelaide, for

his help in the literature search. We would like to

thank Mr Tavik Morgenstern, School of Medical Sci-

ences, University of Adelaide, Australia, for sketching

the diagrams depicted in this manuscript. We also

thank Dr John Currie, senior visiting anaesthetist of

our hospital for his valuable guidance and inputs in

preparing the revision.

Competing interestsNo external funding and no competing interests

declared.

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Appendix Details of the searchstrategy

PubMed(Laryngeal mask*[tw] OR Supraglottic airway*[tw] OR

Extraglottic airway* [tw] OR Supra glottic airway*[tw]

OR Extra glottic airway* [tw] OR Ultra CPV[tw] OR

Ultra clear CPV[tw] OR Ultraflex CPV[tw] OR Aura-

straight[tw] OR Auraonce[tw] OR Aura40[tw] OR

Auraflex[tw] OR Vital seal[tw] OR King LAD[tw] OR

King LAD flexible[tw] OR LMA Classic[tw] OR LMA

unique[tw] OR LMA flexible[tw] OR Cobra PLA perila-

ryngeal airway*[tw] OR Cobra Plus[tw] OR Portex soft

seal[tw] OR SLIPA[tw] OR Streamlined liner*[tw] OR i-

gel[tw] OR LMA-prosea[tw] OR LMA-Supreme[tw] OR

King/VBM LT/Lt-D[tw] OR King/VBM LTS-D[tw] OR

VBM LTS II[tw] OR VBM GLT*[tw] OR Esophageal

tracheal tube[tw] OR Rusch Easy Tube[tw] OR Aura-i

[tw] OR Air-Q/ILA[tw] OR LMA Fastrach[tw] OR

LMA classic excel[tw] OR Baska Mask[tw] OR Guardian



CPV[tw]) AND (Cranial nerves[mh] OR Cranial nerve*

[tw] OR Lingual nerve*[tw] OR Inferior Alveolar

Nerve* [tw] OR Hypoglossal Nerve* [tw] OR Recurrent

Laryngeal Nerve* [tw] OR inferior Laryngeal Nerve*

[tw] OR Glossopharyngeal Nerve* [tw] OR Mental

nerve*[tw] OR Infra-orbital nerve*[tw] OR Infra-orbital

nerve*[tw] OR Cranial nerve injuries[mh] OR Cranial

neuropath*[tw] OR cranial neuropraxia*[tw] OR cra-

nial nerve neuropraxia* [tw] OR sensory loss*[tw] OR

tongue numbness*[tw] OR dysgeusia*[tw] OR taste*

[tw] OR Parageusia*[tw] OR Ageusia*[tw] OR Gusta-

tion [tw] OR Lip numbness[tw] OR Lip swelling[tw] OR

Swollen lip*[tw] OR Dysphagia*[tw] OR Deglutition

Disorder*[tw] OR Swallowing disorder*[tw] OR Dys-

arth*[tw] OR Tongue immobilit*[tw] OR Hoarseness

[tw] OR Stridor[tw] OR Respiratory Aspiration of Gas-

tric Contents[tw] OR Tracheostom*[tw] OR Vocal Cord

Paralys*[tw] OR Vocal cord Pals*[tw] OR Vocal fold

Pals*[tw] OR vocal cord pares*[tw] OR Vocal cord de-

formit*[tw] OR Laryngeal Paralys*[tw] OR Laryngeal

edema*[tw] OR Laryngeal oedema*[tw] OR Dysphonia

[tw] OR Phonation disorder*[tw] OR (lip[tw] AND

scabbing [tw])) AND (Case series [tw] OR Case report*

[tw] OR Case stud*[tw] OR Case histor*[tw])

Embase‘Laryngeal mask’/syn ORsupraglottic next/1 airway*

OR supraglottic next/1 device* OR extraglottic next/1

airway* OR extraglottic next/1 device* OR ‘supra

glottic’ next/1 airway* OR ‘Supra glottic’ next/1

device* OR ‘extra glottic’ next/1 airway* OR ‘extra

glottic’ next/1 device* OR ‘Ultra CPV’ OR ‘Ultra clear

CPV’ OR ‘Ultraflex CPV’ OR Aurastraight OR Au-

raonce OR Aura40 OR Auraflex OR’Vital seal’ OR

‘King LAD’ OR ‘LMA Classic’ OR ‘LMA unique’ OR

‘LMA flexible’ OR ‘Cobra PLA’ OR ‘perilaryngeal air-

way’ OR ‘Cobra Plus ‘ OR ‘Portex soft seal’ OR SLI-

PA OR ‘Streamlined liner of the pharynx airway’ OR

‘i-gel’ OR ‘LMA-proseal’ OR ‘LMA-Supreme’ OR

‘King VBM LT Lt-D’ OR ‘King VBM LTS-D’

OR’VBM LTS II’ OR ‘VBM GLT’ OR ‘gastrolaryngeal

tube’ OR ‘Esophageal tracheal tube’ OR ‘Rusch Easy

Tube’ OR ‘Aura-i’ OR ‘Air-Q ILA’ OR ‘LMA Fast-

rach’ OR ‘LMA classic excel’ OR ‘Baska Mask’ OR

‘Guardian CPV’ AND ‘Cranial nerve’/syn OR ‘glosso-

pharyngeal nerve’/syn OR ‘hypoglossal nerve’/syn OR

‘lingual nerve’/syn OR ‘mandibular nerve’/syn OR ‘max-

illary nerve’/syn OR ‘trigeminal nerve’/syn OR ‘vagus

nerve’/syn OR ‘Inferior Alveolar Nerve’/syn OR

‘recurrent laryngeal Nerve’/syn OR ‘inferior laryngeal’

next/1 nerve* OR mental next/1 nerve* OR ‘mental

nerve’/syn OR ‘infra-orbital nerve’/syn OR ‘infra orbi-

tal’ next/1 nerve* OR ‘infra-orbital nerves’ OR ‘cranial

nerve injury’/syn OR ‘glossopharyngeal nerve injury’/

syn OR ‘hypoglossal nerve injury’/syn OR ‘trigeminal

nerve injury’/syn OR ‘vagus nerve injury’/syn OR Cra-

nial next/1 neuropath* OR cranial next/1 neuroprax-

ia* OR sensory next/1 loss* OR tongue next/1

numbness* OR dysgeusia* OR taste/syn OR ageusia/

syn OR Parageusia* OR lip next/1 numbness* OR lip

next/1 swelling* OR swollen next/1 lip* OR dyspha-

gia/syn OR dysarthria/syn OR Tongue next/1 immobi-

lit*Hoarseness OR Stridor OR ‘Respiratory Aspiration

of Gastric Contents’ OR Tracheostom* OR ‘Vocal

Cord Paralysis’/syn OR ‘Vocal cord Palsies’ OR ‘Vocal

cord’next/1 deformit* OR Laryngeal next/1 (Paralys*

OR edema* OR oedema*) OR Dysphonia/syn OR

Phonation next/1 disorder* OR (lip AND scabbing)

AND (‘Case study’/syn OR ‘Case report’ OR Case

next/1 histor*)



Health & Medicine

Thiruvenkatarajan et al-2015-anaesthesia