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O R I G I N A L A R T I C L E ors_1096 8..14

Characteristics ofpatients referred toaUK trigeminalnerve injury serviceP.P. Robinson

Departmentof Oraland Maxillofacial Medicine andSurgery, Universityof Sheffield,Sheffield,UK

Abstract

Aim: Patients suffering from a persistent sensory disturbance or pain fol-

lowing a trigeminal nerve injury are frequently referred to a specialist

centre for evaluation. This study reports the characteristics of the patients

seen on a designated nerve injury clinic during 2008.

Methods: Information from100 consecutivepatientswas collated, including

demographic details, source of referral, nerve damaged, cause of the injury,

presenceorabsenceofdysaesthesiaandnatureofthetreatment,ifoffered.

Results: There were 70 females and 30 males, with a mean age at presenta-

tion of 42 years (range 2178 years). Sixty-five per cent of referrals were

from a consultant, and patients travelled from a wide geographical distribu-

tion across England, Wales and Ireland. The delay between nerve injury and

referral rangedfrom 1 monthto 5 years. Fifty-sixper cent of thepatients had

sustained an inferior alveolar nerve (IAN) injury and 44% had a lingual

nerveinjury. Most injuries (59%) were causedby lower third molar removal,

but there were numerous other causes, including 10% associated with local

anaesthetic administration. A similar proportion of patients reported symp-

toms of dysaesthesia after lingual nerve (41%) andIAN (45%) injuries.Only

41% of patients were treated (52% of lingual nerve injuries and 32% of IAN

injuries), and this usually involved microsurgical repair (lingual nerve inju-ries)ordecompressionandneurolysis(IANinjuries).

Conclusions: The highly selected population of patients that received ter-

tiary referral to a specialist nerve injury clinic were most commonly female

and 3050 years old. A substantial proportion had dysaesthesia, and these

patients were most likely to be offered treatment.

Keywords:

inferior alveolar nerve, lingual nerve,nerve

injury, nerverepair

Correspondence to:

ProfessorPP Robinson

Departmentof Oraland Maxillofacial Medicine

andSurgery

Schoolof Clinical DentistryClaremont Crescent

Sheffield S10 2TA

UK

Tel.:+44 114 271 7849

Fax:+44 114 271 7863

email: [email protected]

Accepted:27July2010

doi:10.1111/j.1752-248X.2010.01096.x

Clinical relevance

Rationaleforstudy

To understand the characteristics of patients referred toa specialist trigeminal nerve injury clinic for advice and

treatment.

Principlefindings

Patients were most commonly middle-aged females,

and more than 40% were suffering from painful

dysaesthesia. Lower third molar removal was the

commonest cause of injury.

Practical implications

Patients with a trigeminal nerve injury who develop

dysaesthesia or show limited signs of early recovery

should be referred to a specialist centre without delay.Only about 40% will be deemed suitable for surgical

intervention.

Introduction

While trigeminal nerve injuries are relatively common,

experience in the management of patients who may

benefit from surgical intervention is often limited. As a

OralSurgeryISSN 1752-2471

8 OralSurgery 4 (2011)814.

2010JohnWiley&SonsA/S

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result, manypatientsare referred to specialistcentres for

advice and treatment. This article describes the charac-

teristics of patients seen by the author in one such

centre,inSheffield,UK,duringthecalendaryear2008.

The commonest cause of problematic trigeminal

nerve injury appears to be iatrogenic damage during

oral surgical procedures, such as the removal of lowerthird molars. For this procedure, the incidence of

lingual nerve injury is approximately 7% (but varies

with the surgical technique employed), and the inci-

dence of inferior alveolar nerve (IAN) injury is

approximately 4%1. In 20082009, in the National

Health Service hospital service in England alone,

68 343 third molar removals were recorded2. If we

assume that approximately two-thirds of these were

lower third molars3, the incidence of nerve injury

describedabovewould resultin over 3000 lingual nerve

injuries and nearly 2000 IAN injuries per year. Of these,

most are followed by recovery of normal sensation

within the first few weeks after the injury, but approxi-

mately0.5% of operations1 lead to a permanentsensory

disorder (i.e. approximately 230 lingual nerve injuries

and 230 IAN injuries in England per year). Some of

these patients find the symptoms sufficiently distressing

that they seek further treatment, and this study has

determined the characteristics and specific complaints

of that group. It is important to note that the character-

istics described do not represent those of the whole

population of patients that suffer a nerve injury, just

the highly selected group that have sought further help

and have pursued referral to a centre with a specialist

interest in this problem.Others have reported observations on similar popu-

lations elsewhere. For example, Pogrel and Thamby4

reported on 163 consecutive patients attending their

unit in San Francisco, USA, and Tay and Zuniga5

described the clinical characteristics of 59 patients

referred to a university centre in Chapel Hill, USA,

over a 10 month period. A larger study by Hillerup6

described the signs, symptoms and functional status of

449 injuries seen in Copenhagen, Denmark, over an

18 year period. Comparisons will be made with obser-

vations at these other centres.

Materialsandmethods

Information was obtained relating to all patients

attending the authors trigeminal nerve injury clinic

during the calendar year 2008. Surprisingly, but con-

veniently, this gave data from exactly 100 consecutive

patients. All patients attending the clinic had demo-

graphic details, nerve damaged, date and cause of the

injury, symptoms, responses to specific questions and

results of sensory testing, recorded on a pro forma.

These prospectively obtained data were combined with

information in the medical records regarding grade and

site of the referring practitioner, the delay between

initial injury and referral, and the nature of the treat-

ment undertaken, if offered.

Particular note wastakenof theproportion of patientsthat were suffering from the painful symptoms of dysa-

esthesia (defined as an unpleasant abnormal sensation,

whether spontaneous or evoked7). This diagnosis was

based on the patients report of spontaneous or evoked

pain from the affected area, and/or evidence from

sensorytestsrevealingallodyniaorhyperalgesia.

Details of the sensory testing protocol have been

reported elsewhere8. The outcome of the treatment

methods used has also been reported previously, so will

not be repeated here9,10.

ResultsOf the 100 patients, 70 were female and 30 were male.

The age distribution was similar for females (mean age

41 years, range 2178 years) and males (mean age

42 years, range 2375 years) and is shown in Figure 1.

Referrals were received from a wide geographical dis-

tribution across England, Wales and Ireland, and the

patient locations are shown on a map in Figure 2. A

high proportion of the referrals (65%) were from a

consultant (usually an oral and maxillofacial surgeon)

with the remainder being from an SAS (Staff Grade or

Associate Specialist) grade (12%), specialist registrar

(2%), Senior House Officer (7%), General DentalPractitioner (13%) or General Medical Practitioner

(1%). The delay between the time of injury and referral

2029 3039 4049

Age (years)

5059

30

FemalesMales

25

20

15

Num

berofpatients

10

5

06069 7079

Figure 1 Age distribution: the age distribution of the 70 female and 30

malepatientsseen during2008.

Robinson Characteristicsof nerve injury patients

9OralSurgery 4 (2011) 814.


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to the clinic varied widely and is shown in Figure 3.

This reveals that 30% of the referrals were made within

the first 3 months after the injury, 47% within

6 months and 71% within a year, but some referrals

were delayed by as much as 5 years.

The nerves that had sustained an injury are shown inFigure 4. In this series, 44% of patients had sustained a

lingual nerve injury and 56% had sustained an IAN

injury, and this included six patients who had an injury

to more than one nerve. Within these groups, 41% of

the lingual nerve injury patients and 45% of the IAN

injury patients had symptoms and/or signs consistent

with the diagnosis of dysaesthesia (Fig. 4). The cause

of the injury varied widely, as shown in Figure 5,

although by far, the commonest cause was the removal

of lower third molars (59%). Local anaesthetic admin-

istration resulted in 10% of the injuries, and man-

dibular implants caused 5% of the injuries. Despite the

fact that damage to the IAN commonly occurs in man-

dibular fractures, and the infraorbital nerve is com-

monly damaged in zygomatic fractures, these injuriesled to referral of only 4% and 3% of cases, respectively.

Based on previously described protocols11,12, the level

of symptoms and the anticipated outcome of surgical

intervention9,10, a decision was made on whether or not

to offer treatment. The proportion of patients with a

lingual nerve injury that proceeded to treatment was

52%, whereas the proportion with an IAN injury that

proceeded to treatment was only 32%. This difference

in part reflects the relative effectiveness of surgical

Figure 2 Patient location: the home location of the patients, indicating the geographical spread of referrals. The number in each red dot indicates the

numberof patientsfrom thatlocation.Map reproduced fromOrdnanceSurveymap databy permissionof theOrdnanceSurvey Crown copyright2010.

Characteristicsof nerve injury patients Robinson



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treatment of these nerves in the Sheffield unit9,10. Fur-

thermore, treatment of an IAN injury was more likely

to be offered in the presence of dysaesthesia, and as

a result, 14 of the 17 patients who underwent IAN

decompression and neurolysis were suffering from

dysaesthesia. The types of treatment undertaken onpatients seen during 2008, and the proportion suffering

from dysaesthesia, are shown in Figure 6A and B.

Discussion

Demographics

The patient population referred to a specialist trigemi-

nal nerve injury clinic does not fully reflect the demo-

graphics of patients undergoing lower third molar

removal, although this is the commonest cause of the

injury. Details of patients having third molars removed

as an inpatient in England in 200820092 show that

third molar removal was more frequently undertaken

in females (62% of procedures) than males (38%), and

the average age was 30 years. In the present study, of

the highly selected population of patients that received

tertiary referral to a specialist trigeminal nerve injury

clinic, an even higher proportion was female (70%)

and the average age was 41 years. Thus, the referredpatients were commonly middle-aged females. Similar

patterns have been seen in previous reports, with the

Chapel Hill study having 61% females and a mean age

of 40 years5, and the Copenhagen study having 73%

females and a median age of 36 years6. The report by

Pogrel and Thamby4 also found a preponderance of

females (77%) but found a lower mean age of only

28 years. While this sex distribution probably results

from females being more likely to seek treatment, there

is also some clinical evidence to suggest that a close

relationship between impacted third molars and the

mandibular canal may be more common in women13,

rendering the IAN at greater risk.

Referral

Most of the referred patients had been seen by their

local hospital oral surgery service initially, although

the surgery that gave rise to the nerve injury may

have been undertaken elsewhere. As a result, 65% of

the referrals were from consultants, mostly oral and

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maxillofacial surgeons. In order to obtain specialist

advice and possible treatment, patients were prepared

to travel substantial distances, emphasising the signi-

ficance of the symptoms. Some of the delays before

referral were too long, even up to 5 years, and there aremany factors that could have led to these delays.

Current guidance suggests that lingual nerve or IAN

injuries resulting from third molar removal should

be monitored for approximately 3 months to assess

spontaneous recovery before deciding whether or not

surgical intervention is needed11,12,14. Should there be

little evidence of recovery by that stage, referral to a

unit with a specialist interest in the management of

trigeminal nerve injuries is appropriate.

Causeof injury

In the present study, most injuries (59%) were caused

by third molar removal, with the next most common

cause being local anaesthetic administration (10%).

Very similar figures have been reported elsewhere. For

example, of 59 patients referred to a university centreat Chapel Hill, USA, 52% resulted from lower third

molar removal, 12% from local anaesthetic injec-

tions, 12% from orthognathic surgery and 11% from

implants5. In the San Francisco study, 53% of the inju-

ries were caused by third molar removal and 21% by

local anaesthetic administration4. Hillerup 6 confined

his study to iatrogenic injuries, but found 71% to result

from third molar surgery and 17% from local anaes-

thetic administration. Thus, the cause of injury seems

broadly similar in different centres evaluated in Europe

and North America.

Of the 10 injuries associated with local anaesthetic

administration in the present study, six involved the

lingual nerve and four involved the IAN; a higher like-

lihood of this type of damage to the lingual nerve has

been reported by Hillerup and Jensen15. These authors

also demonstrated the increased frequency of this

problem since the introduction of Articaine, suggesting

a neurotoxic effect15. Pogrel et al.16 indicated that 9

of their 12 cases of local anaesthetic administration

injuries involved the lingual nerve, two involved the

IAN and one was apparently confined to the chorda

tympani. They reported that just seven (58%) of their

patients experienced an electric shock sensation at the

time of injection, showing that the absence of this signshould not preclude the diagnosis of a local anaesthetic

administration injury.

A relatively uncommon cause of IAN injury is

chemical or mechanical damage during root canal

treatment. Only one such patient was seen in the

present series, and surgical removal of extruded mate-

rial within the mandibular canal was undertaken. In a

series of 61 patients with this problem reported by

Pogrel17, optimal recovery appeared to follow surgical

exploration and removal of any material within 48 h

of the initial treatment. This early intervention can

be extremely difficult to achieve for practical reasonsand is dependent upon immediate referral by the

endodontist to an appropriate specialist centre.

It is interesting that few of the many trigeminal

nerve injuries caused by facial bone fractures are

referred for assessment at a specialist nerve injury

clinic. The demographics of this population is very

different (often young males who have been

assaulted), but the nature of the nerve injury itself

may also differ; fractures are perhaps more likely to

(A)

(B)

Figure 6 Treatment: the types of intervention undertaken on patients

seen during the period evaluated for (A) lingual nerve injuries and (B) infe-

rioralveolarnerve injuries. RCT, removalof extrudedroot fillingmaterial.




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lead to crush or minor traction injuries rather than the

partial or complete section injuries that can result

from iatrogenic damage. Recovery from a crush injury

is likely to be more successful, with less risk of the

development of dysaesthesia1.

Nerve damaged

In the Sheffield clinic, IAN injuries were commonest

(56% of patients), and 44% had a lingual nerve injury.

Again, this is similar to the pattern of referrals else-

where, as at the Chapel Hill centre, 64% of patients

had an IAN injury and 29% had a lingual nerve injury5.

Conversely, in Hillerups Copenhagen study, 58% were

lingual nerve injuries and just 33% IAN injuries6, and

in Pogrel and Thambys4 study, 58% had lingual nerve

injuries and 52% IAN injuries, as some patients had

more than one nerve damaged.

Dysaesthesia

A substantial proportion of the referred patients

had the unpleasant painful sensations of dysaesthesia,

and this proportion was similar for both lingual nerve

(41%) and IAN (44%) injuries. In the Copenhagen

study, only 17% of patients were diagnosed as suffer-

ing from dysaesthesia6, and in the Chapel Hill study5,

a similar figure of 15% of the patients had neuro-

pathic pain, but all of these had sustained an IAN

injury. In a study of 227 Swedish patients who had

been awarded compensation as a result of a trigemi-

nal nerve injury, approximately 20% suffered fromperiods of pain in the affected area18. The higher inci-

dence of reported pain in the present study is difficult

to explain, but there may be cultural differences in

describing subjective experiences. Patients often have

difficulty in analysing their symptoms, sometimes

reporting them as unpleasant and uncomfortable,

but not painful. A comparably high incidence of

neuropathic pain (45%) was reported by Jskelinen

and colleagues19 when describing patients referred

for neurophysiological evaluation after a trigeminal

nerve injury. Surveys on the general population

suggest that patients with neuropathic pain aremore likely to be female and slightly older than the

average20, and this is another possible explanation for

the distribution of patients seen in the present study.

Treatment

When taking into account likely surgical outcomes, less

than half of the referred patients (41%) were consid-

ered appropriate for treatment. This is similar to the

proportion in the study by Tay and Zuniga5, where 46%

were offered surgery, and it was undertaken in a third;

this suggests that similar criteria are being employed in

the two units. Of the 261 patients with lingual nerve

injuries described by Hillerup and Stoltze21, 86 (33%)

underwent surgical intervention, and this included

two patients where external neurolysis was the chosenprocedure. This latter procedure is usually only con-

sidered appropriate if a substantial proportion if the

nerve remains intact. In Pogrel and Thambys study 4,

only 17% of their 163 patients were offered surgery,

and it was undertaken in just 9%; this might suggest

that their study initially included more patients with

minor injuries, and this might also explain the younger

mean age of their patients as described above.

The patients offered treatment in the present study

were most likely to be those with neuropathic pain.

Analysis of our outcomes previously has shown that

the proportion of patients with some pain may not

reduce9, but the level of the symptoms will often

decline10; this has also been reported in other studies22.

References

1. Holland GR,RobinsonPP. Peripheral nerve damage and

repair. In:Harris M, Edgar M, MeghjiS, editors: Clinical

Oral Science. Oxford, UK: Butterworth-Heinemann,

1998:27489.

2. HospitalEpisodeStatistics,200809Inpatient andOut-

patient Datafor MainProceduresand Interventions.

2009.AvailablefromURLhttp://www.hesonline.

nhs.uk[accessed9April2010].3. Dhariwal DK,Goodey R, Shepherd JP.Trends in oral

surgery in England andWales 19912000. Br Dent J

2002;192:63945.

4. PogrelMA, ThambyS. Theetiologyof altered sensation

in the inferior alveolar, lingual andmental nervesas a

resultof dentaltreatment. J Calif Dent Assoc J 1999;27:

5318.

5. Tay ABG, ZunigaJR. Clinical characteristicsof

trigeminalnerve injury referrals to a university

centre. IntJ Oral Maxillofac Surg 2007;36:

9227.

6. Hillerup S. Iatrogenic injuryto oral branches of the

trigeminal nerve:records of 449cases. Clin OralInvestig 2007;11:13342.

7. International Association forthe Study of Pain

Terminology. 2010.Available from URL http://www.

iasp-pain.org/AM/Template.cfm?Section=Pain_

Defi . . . isplay.cfm&ContentID=1728#Dysesthesia

[accessed28 June 2010].

8. Robinson PP,SmithKG, Johnson FP,Coppins DA.

Equipment and methods for simple sensory testing.

Br J Oral Maxillofac Surg 1992;30:3879.

Robinson Characteristicsof nerve injury patients

13OralSurgery 4 (2011) 814.


7/26/2019 j.1752-248X.2010.01096.x

7/7

9. Robinson PP,LoescherAR, Smith KG.A prospective

quantitativestudyon the clinicaloutcome of lingual

nerve repair. Br J Oral Maxillofac Surg 2000;38:

25563.

10. RobinsonPP, Yates JM,SmithKG. A prospective,

quantitativestudy on theclinicaloutcome of inferior

alveolar nerve decompression and neurolysis. Oral

Surg 2008;1:3544.

11. Loescher AR,Smith KG,RobinsonPP. Nerve damage

andthird molar removal. Dent Update

2003;30:37582.

12. RobinsonPP, Loescher AR,Yates JM,SmithKG.

Current management of damage to the inferior alveolar

andlingual nervesas a resultof removal of third molars.

Br J Oral Maxillofac Surg 2004;42:28592.

13. Howe GL,Poyton HG.Prevention of damage to

the inferiordental nerve duringthe extraction of

mandibular third molars. Br Dent J 1960;109:

35563.

14. Hillerup S, Stoltze K. Lingual nerve injuryin third

molar surgery. I. Observations on recovery of sensation

with spontaneous healing.Int J Oral Maxillofac Surg

2007;36:8849.

15. Hillerup S, JensenR. Nerve injury caused by

mandibular block analgesia. Int J Oral Maxillofac

Surg 2006;35:43743.

16. Pogrel MA,BryanJ, RegeziJ. Nerve damage associated

with inferior alveolar nerve blocks. J Am Dent Assoc

1995;126:11505.

17. PogrelMA. Damage to theinferioralveolar nerve

as the result ofrootcanal therapy.J AmDentAssoc

2007;138:659.

18. Sandstedt P, Sorensen S. Neurosensory disturbances

of thetrigeminal nerve:a long-termfollow-up of

traumatic injuries. J Oral Maxillofac Surg

1995;53:498505.

19. Jskelinen SK, Teerijoki-Oksa T, Forssell H.

Neurophysiologic and quantitative sensory testing in

the diagnosis of trigeminal neuropathy and

neuropathic pain.Pain 2005;117:34957.

20. Torrance N, Smith BH, Bennett MI,Lee AJ.The

epidemiology of chronic pain of predominantly

neuropathic origin. Results from a general

population survey. J Pain 2006;7:2819.

21. Hillerup S, Stoltze K. Lingual nerve injury. II.

Observations on sensory recovery after

micro-neurosurgical reconstruction.Int J Oral

MaxillofacSurg 2007;36:113945.

22. Gregg JM.Studies of traumaticneuralgia in the

maxillofacial region: symptom complexes and

response to microsurgery. J Oral Maxillofac Surg

1990;48:13540.




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