Chiari Malformation

Presented byAbdulgadir F. Bugdadi

Types• Consists of 4 types. Probably unrelated to each other.

TYPE 1 CHIARI MALFORMATION

Epidemiology• Age of presentation ( 12 – 73) average age is 40 years.

Adults

• Slight female preponderance.

Feature• Heterogeneous entity but the common feature is ;

Impaired CSF Circulation through Foramen magnum.

Components1. Caudal displacement of Cerebellum with tonsillar herniation below

foramen magnum.( > 5mm below the foramen magnum , not essential and nor diagnostic).

2. Syringomyelia (30%-70%)….

3. Hydrocephalus (7% - 9% in patients with 1&2)

Etiology• Different etiologies can be with it;

1. Small posterior fossa ….

2. Intracranial space occupying lesions ..

3. Lumboperitoneal shunt or multiple LP. “acquired, usually asymptomatic”.

4. Arachnoid web or scar or fibrosis around brainstem and tonsils around FM.

5. Abnormalities of upper cervical spines ….

6. Ehlers - Danlos syndrome.

7. Craniosynostosis.

SymptomsEtiology ofSymptoms

Compression ofBrain stem

Hydrocephalus

Syringomyelia

% Symptom

69% Pain (H/A ‘34%’, neck, gridle, arm, leg)

56% Weakness

52% Numbness

40% Loss of temperature sensation

40% Unsteadiness

15% Painless burns

13% Diplopia

8% Dysphasia

7% Tinnitus

5% Vomiting

4% Dysarthria

3% E

Dizziness, Deafness, Fainting, Facial numbness

Asymptomatic 15% – 30%.

SignsEtiology of signs

Foramen magnum compression syndrome

(22%)

Central Cord Syndrome(65%)

Cerebellar syndrome(11%)

Ataxia, corticospinal and sensory deficits, cerebellar signs and lower cranial nerve palsies.

Loss of pain and temperature sensation, segmental weakness, syringomyelic syndrome or lower cranial nerve palsies ‘11%’.

Ataxia, nystagmus (downbeat), dysarthria.

Normal neurologic exam 10%

Imaging• MRI ;

Diagnostic test of choice.Abnormalities that can be seen :1. Tonsillar herniation.2. Hydrosyringomyelia (20% - 30%).3. Ventral brain stem compression.4. Other findings ; Hydrocephalus or empty sella.

Cont.

Other imaging

• Cine MRI “CSF flow study”…

• Myelography…

• CT…

Treatment• Surgical management.

• Goal of surgery ;Decompress the brain stem an reestablish normal CSF flow at the craniocervical junction.

• Indication of surgery ;- Symptomatic.- Best response…- symptomatic & stable for years…

• Surgery performed ;

1. Posterior fossa decompression (suboccipital craniectomy) +/-2. Dural patch grafting.3. Laminectomy of C1 (sometimes C2 or C3).

TYPE 2 (ARNOLD) CHIARI MALFORMATION

Feature

1. Caudally displaced cervicomedullary junction, pons, 4th ventricle and medulla.

2. Cerebellar tonsils located at or below foramen magnum.

Usually associated with myelomeningocele and often accompanied by hydrocephalus.

Theory of pathophysiology

• Primary dysgenesis of the brainstem with multiple other developmental anomalies. Not the result of tethering by the associated myelomeningocele.

Onset is rare in adulthood

SymptomsSymptoms

Dysphagia (69%)

Apneic spells (58%)

Stridor (56%)

Aspiration (40%)

Arm weakness (27%)

Opisthotonos (18%)

Nystagmus

Facial weakness

Weak or absent cry

Etiology of symptoms

Brain stem and lower cranial nerve dysfunction

Imaging

• MRI ;A. Primary findings:

1. “Z” bend deformity of medulla.2. Cerebellar peg.3. Tectal fusion “Tectal beaking”.4. Interthalamic adhesions.5. Elongation/cervicalization of medulla.6. Low attachement of tentorium.

B. Associated findings ;1. Hydrocephalus.2. Syringomyelia at cervicomedullary junction.3. Trapped 4th ventricle.4. Cerebellomedullary compression.5. Agenesis/dysgenesis of corpus callosum.

Treatment1. Insert CSF shunt for hydrocephalus (or check functioning of an existing

shunt).

2. Surgical decompression is recommended for : (Argument)

A. Neurogenic dysphagia.B. Neurogenic stridor.C. Apneic spells.

Note:Before recommending decompression always make sure that the patient has a functioning shunt.

• Chiari type 3;1. displacement of posterior fossa structures with cerebellum herniated through foramen magnum into cervical canal + high cervical or suboccipital encephalomeningocele.2. Usually incompatible with life.

• Chiari type 4;Cerebellar hypoplasia without cerebellar herniation.

END

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