Chiari Malformation

(1)

In 1891, Chiari first described a dysplasia of the nervous sys- tem consisting of herniation of the cerebellar tonsils into foramen magnum. There are three types of Chiari malformation.

The commonest ones are type I and type II, the latter has been named the Arnold-Chiari malformation. (De Reuck, 1976)

GENETICS/BASIC DEFECTS

1. Classification of Chiari malformations according to the severity

a. Type I (the milder malformation)

i. Ectopia of the cerebellar tonsils (caudal herniation of the cerebellar tonsils and inferior cerebellum through the foramen magnum)

ii. Usually an isolated feature encountered in adults b. Type II (the more severe malformation)

i. Downward displacement of the cerebellar medulla and fourth ventricle into the spinal canal ii. Almost always associated with meningomyelocele iii. May be associated with polygyria, cortical het- erotopia, and dysgenesis of the corpus callosum c. Type III (the most severe malformation)

i. Downward displacement of most of the cerebellum into a high cervical/low occipital encephalocele ii. Malformation consisting of anatomical anom-

alies typical of Chiari type II malformation with those of a high cervical/occipital encephalocele 2. Acquired Chiari I malformation caused by conditions

leading to increased intracranial pressure a. Head injury

b. Hydrocephalus c. Craniosynostosis

3. Brainstem dysfunction, sensory disturbance, and motor loss caused by impaction of the tonsils against the cervi- comedullary structures

CLINICAL FEATURES

1. Patients with Chiari I malformation a. Asymptomatic in majority of patients b. General symptoms

i. Headache ii. Fatigue iii. Memory loss

iv. Pressure on the neck v. Back pain

vi. Insomnia vii. Poor circulation viii. Nausea

ix. Menstrual problems x. Sexual alterations xi. Hypothermia xii. Bronchial aspirations

xiii. Respiratory alterations xiv. Drop attacks

xv. Rare reports of sudden death c. Ocular symptoms

i. Loss of vision

ii. Intolerance of bright light iii. Diplopia

d. Otolaryngologic symptoms i. Vestibular manifestations

a) Imbalance b) Swaying c) Dizziness d) Positional vertigo e) Spontaneous vertigo f) Nystagmus

g) Hearing loss h) Tinnitus

ii. Alterations of cranial pairs a) Dysphagia

b) Dysphonia

c) Alterations in tongue mobility d) Loss of smell

e) Facial hyposthesia iii. Sleep apnea

e. Cerebellum compression symptoms i. Ataxia

ii. Nystagmus iii. Gait difficulties

iv. Opisthotonos v. Horner’s syndrome

vi. Paralysis of the last cranial nerves vii. Hypotonia

viii. Trembling ix. Dysarthria x. Dysmetria

f. Associated CNS anomalies

i. Stenosis of the aqueduct of Silvia ii. Meningomyelocele

iii. Syringomyelia (cystic dilation of the spinal cord) g. Symptoms associated with syringomeyelia

i. Known to accompany 50% to 70% of patients with Chiari I malformations

ii. Obstructed cerebrospinal fluid at the site of cerebellar tonsillar herniation shows perivascular movement of CSF from the spinal subarachnoid space into the spinal cord with each Valsalva maneuver and cause syringomyelia

iii. Tingling, hyposthesia, and burning sensation in the extremities

iv. Thermalgesic anesthesia v. Alteration in muscular reflexes vi. Areflexia

vii. Alteration of kinesthesia 157

Chiari Malformation

(2)

158 CHIARI MALFORMATION

viii. Motor skill dysfunction

ix. Headache or nonradicular pain in the shoulder, back, and limbs

x. Headache usually suboccipital and upper cervical in location and is exacerbated by Valsalva maneuvers

xi. Associated with the development of a painful, rapidly progressive, or left-curving scoliosis xii. Recent reports of spontaneous radiographic

improvement of childhood Chiari malformations and syringomyelia

2. Chiari I malformation in children and adolescents a. Natural history of an asymptomatic Chiari I malfor-

mation in children i. Not well understood

ii. Rarely reported to resolve spontaneously iii. Asymptomatic at the time of diagnosis in many

children

iv. Degree of tonsillar ectopia correlating well with the presence of neurologic signs and symptoms v. Rare reports of sudden death

b. Group I (asymptomatic)

i. Age at diagnosis: 3 months to 17 years ii. Associated conditions

a) Hydrocephalus

b) Craniofacial syndromes c) Epilepsy

d) Occult spinal dysraphism c. Group II (brain stem compression)

i. Age at diagnosis: 7 months to 26 years ii. Associated conditions

a) Craniofacial syndromes b) Hydrocephalus

c) Precocious puberty iii. Symptoms

a) Neck pain b) Vertigo c) Headache d) Numbness

e) Swallowing difficulties f) Apnea

g) Opisthotonos h) Brachialgia

i) Hyposthenia j) Spasticity k) Hemifacial pain

d. Group III (presence of syringomyelia). Symptoms are:

i. Numbness ii. Sensory loss iii. Neck pain

iv. Vertigo v. Scoliosis vi. Hyposthenia vii. Headache

viii. Muscle hypotrophy ix. Swallowing difficulties

x. Limb pain

3. Patients with Chiari II malformation

a. Almost invariably associated with myelomeningocele (90%)

b. Brain stem signs in 20% of patients with Chiari II malformation in children and adolescence

i. Vertigo

ii. Bioccipital headache iii. Cerebellar dysfunction

iv. Progressive paresis of the arms 4. Patients with Chiari III malformation

a. Rarest of the Chiari malformations

b. Associated with a high cervical or occipital encephalocele

c. Prognosis for nearly all reported patients i. Various degree of developmental delay ii. Epilepsy

iii. Hypotonia iv. Spasticity

v. Upper and/or lower motor neuron deficits vi. Lower cranial nerve dysfunction

d. CNS anomalies usually observed in an occipital encephalocele

i. A small cranial fossa

ii. Caudal displacement of cerebellar tonsils and vermis

iii. Medullary kinking iv. Tectal beaking

v. Obvious hydrocephalus

DIAGNOSTIC INVESTIGATIONS

1. CT or MRI

a. Chiari I malformation

i. Incidental detection in asymptomatic individuals ii. Herniation of the tonsils >5 mm below the fora-

men magnum on MRI considered diagnostic b. Chiari II malformation

i. Caudal cerebellum (100%)

ii. Kinking of medulla on spinal cord (79%) iii. Elongation of brainstem and low medulla,

stretched aqueduct and fourth ventricle (75%) iv. Beaking of quadrigeminal plate (60%)

v. Large massa intermedia (55%) vi. Large fourth ventricle (25%) vii. Hydromyelia (15%)

c. Chiari III malformation

i. An occipitocervical meningoencephalo-cele pro- truding through a bony defect involving the lower occipital squama and/or the posterior arch of the first cervical vertebrae

ii. A small posterior cranial fossa with low tentorial attachment

iii. Scalloping of the clivus

iv. Massive herniation of the hypoplastic cerebellar structures into the malformation

v. Beaking of the tectal plate

vi. Dysgenesis of the corpus callosum

vii. Severe ventricular dilatation (hydrocephalus) 2. Brainstem auditory evoked potentials (BAEP)

(3)

CHIARI MALFORMATION 159

a. Consistently abnormal in symptomatic Chiari II malformation

b. Showing a positive predictive value of 88% in pre- dicting central neurologic sequelae in newborns and infants

GENETIC COUNSELING

1. Recurrence risk

a. Patient’s sib: not increased b. Patient’s offspring: not increased 2. Prenatal diagnosis

a. Prenatal ultrasonography

i. Classic ‘lemon and banana’ signs, the gold standard in the early screening of Chiari II malformation

ii. Clivus-supraocciput angle below 5th centile of nomogram in cases of Chiari II malformation b. Prenatal MRI: Chiari III malformation diagnosed dur-

ing third trimester using single shot fast spin echo sequence to avoid motion artifact

3. Management

a. Chiari I malformation

i. Conservative treatment for asymptomatic patients ii. Main treatment consisting of decompressing the

structures trapped in the foramen magnum a) Suboccipital craniectomy with or without

dural patch grafting and cervical laminec- tomies: the most often used procedure b) Syringosubarachnoid shunt when indicated iii. Shunting of hydrocephalus

iv. Major preexisting sensory or motor deficits:

poor prognosticators for functional recovery b. Chiari II (Arnold-Chiari) malformation

i. Seen most often in children with myelomeningocele

ii. Shunting of hydrocephalus often resolves brainstem symptoms and surgical decompression may not be necessary

iii. Surgical decompression of posterior fossa and upper cervical spine may be required if brainstem compression symptoms remain after shunting iv. Surgical intervention indicated to prevent further

deterioration of the motor function and to dimin- ish the progress of spasticity and scoliosis from tethered cord syndrome

c. Chiari III malformation

i. Primary closure of the malformation: usually the treatment of choice

ii. CSF shunting of the associated hydrocephalus postponed to a later phase

iii. Neonates often require intensive care treatment for the associated severe respiratory distress

REFERENCES

Aribal ME, Gurcan F, Aslan B: Chiari III malformation: MRI. Neuroradiology 38:184–186, 1996.

Bindal AK, Dunsker SB, Tew JM: Chiari I malformation: classification and management. Neurosurgery 37:1069–1074, 1995.

Caldarelli M, Rea G, Cincu R, et al.: Chiari type III malformation. Childs Nerv Syst 18:207–210, 2002.

Cama A, Tortori-Donati P, Piattelli GL, et al.: Chiari complex in children.

Neuroradiological diagnosis, neurosurgical treatment and proposal of a new classification. Eur J Pediatr Surg 5 (Suppl):35–38, 1995.

Castillo M, Quencer RM, Dominquez R: Chiari III malformation: imaging features. AJNR 13:107–113, 1992.

D’Addario V, Pinto V, Del Bianco A, et al.: The clivus-supraocciput angle: a useful measurement to evaluate the shape and size of the fetal posterior fossa and to diagnose Chiari II malformation. Ultrasound Obstet Gynecol 18:146–149, 2001.

Dauser RC, Dipietro MA, Venes JL: Symptomatic Chiari I malformation in childhood: a report of 7 cases. Pediatr Neurosci 14:184–190, 1988.

De Barros MC, Farias W, Ataide L, et al.: Basilar impression and Arnold Chiari malformation. A study of 66 cases. J Neurol Neurosurg Psychiatry 31:

596–605, 1968.

De Reuck J, Theinpont L: Fetal Chiari’s type III malformation. Child’s Brain 2:85–91, 1976.

Dure LS, Percy AK, Cheek WR, et al.: Chiari type I malformation in children.

J Pediatr 115:573–576, 1989.

Dyste GN, Menezes AH, Van Gildrer JC: Symptomatic Chiari malformations.

J Neurosurg 71:159–168, 1989.

Elster AD, Chen MYM: Chiari I malformations: clinical and radiologic reap- praisal. Radiology 183:347–353, 1992.

Gálvez MJN, Rodrigo JJF, Liesa RF, et al.: Otorhinolaryngologic manifestations in Chiari malformation. Am J Otolaryngol 23:99–104, 2002.

Gammal TE, Mark EK, Brooks BS: MR imaging of Chiari II malformation.

AJNR Am J Neuroradiol 35:1037–1044, 1987.

Genitori L, Peretta P, Nurisso C, et al.: Chiari type I anomalies in children and adolescents: minimally invasive management in a series of 53 cases.

Childs Nerv Syst 16:707–718, 2000.

Häberle J, H¸lskamp G, Harms E, et al.: Cervical encephalocele in a new- born—Chiari III malformation. Case report and review of the literature.

Childs Nerv Syst 17:373–375, 2001.

Koehler J, Schwarz M, Urban PP, et al.: Masseter reflex and blink reflex abnor- malities in Chiari II malformation. Muscle Nerve 24:425–427, 2001.

Lee R, Tai K, Cheng P, et al.: Chiari III Malformation: Antenatal MRI Diagnosis. Clin Radiol 57:759, 2002.

Milhorat TH, Chou MW, Trinidad EM et al.: Chiari I malformation redefined:

clinical and radiographic findings for 364 symptomatic patients.

Neurosurgery 44:1005–1017, 1999.

Mohr PD, Strang FA, Sambrook MA, et al.: The clinical and surgical features in 40 patients with primary cerebellar ectopia (adult Chiari malformation). Q J Med 46:85–96, 1977.

Nagib MG: An approach to symptomatic children (ages 4–14 years) with Chiari type I malformation. Pediatr Neurosurg 21:31–35, 1994 Naidich TP: Cranial CT signs of the Chiari II malformation. J Neuroradiol

8:207–227, 1981.

Naya Galvez MJ, Fraile Rodrigo JJ, Liesa RF, et al.: Otorhinolaryngologic manifestations in Chiari malformation. Am J Otolaryngol 23:99–104, 2002.

Paul KS, Lye RH, Strang FA, et al.: Arnold-Chiari malformation. Review of 71 cases. J Neurosurg 58:183–187, 1983.

Rauzzino M, Oakes WJ: Chiari II malformation and syringomyelia. Neurosurg Clin N Am 6:293–309, 1995.

Ventureyra EC, Aziz HA, Vassilyadi M: The role of cine flow MRI in children with Chiari I malformation. Childs Nerv Syst 19:109–113, 2003.

Weinberg JS, Freed DL, Sadock J, et al.: Headache and Chiari I malformation in the pediatric population. Pediatr Neurosurg 29:14–18, 1998.

(4)

160 CHIARI MALFORMATION

Fig. 2. A patient with multiple congenital anomalies (mental retarda- tion, flat facial plane, epicanthus inversus, blepharophimosis, cataracts, nystagmus, elbow flexion contractures, and vertical talus) with Chiari I malformation (MRI of the brain).

Fig. 1. Sagittal section of a neonate with a large ruptured lumbar meningomyelocele. Arnold-Chiari malformation is evident: the brain stem and lower portion of cerebellum herniate through the foramen magnum and overlap the cervical cord which is severely flattened.

The brain shows hydrocephalus.

Fig. 3. A 28-year-old female with Chiari I malformation with normal phenotype but complaining headache, dizziness, and neck pain worsen by pregnancy.