Pediatric Database (PEDBASE)

Discipline: CNS

Last Updated: 5/21/94

ENCEPHALOCELE

DEFINITION:

A neural tube defect affecting the skull resulting in the herniation of the meninges and portions of the brain through a bony midline defect in the skull.

EPIDEMIOLOGY:

incidence: 1/10th as common as spinal neural tube defects
age of onset:
- newborn
risk factors:
- multifactorial inheritance pattern
associated anomalies:

1. Syndromes

Dandy-Walker Syndrome
Klippel-Feil Syndrome
Meckel-Gruber Syndrome
- rare autosomal recessive disorder
- occipital encephalocele
- associated with microcephaly, holoprosencephaly, cleft lip or palate, polydactyly, abnormal genitalia, polycystic kidneys

2. Malformations

Arnold-Chiari malformation, porencephaly, agenesis of the corpus callosum, myelodysplasia, optic nerve dysplasia, cleft palate

PATHOGENESIS:

1. Background

two major forms of dysraphism affecting the skull:

1. Cranial Meningocele

consists of a CSF-filled meningeal sac only
skull equivalent of a spinal meningocele

2. Cranial Encephalocele

portions of the brain found in the herniated meningeal sac include cerebral cortex, cerebellum, brainstem, and/or ventricles
neural tissue within encephalocele is often abnormal
the amount of compromised and deformed neural tissue determines the extent of cerebral dysfunction - brain tissue not extending into the encephalocele may be structurally and functionally abnormal
areas/types of encephaloceles:

1. Notencephaloceles (75%)

extend from the occipital region at or below the inion

2. Sincipital Encephaloceles (25%)

extend from the orbits, nose or forehead
occur most frequently in Asians
basal and transsphenoid encephaloceles:
- rare, arise between the ethmoid and sphenoid bones and may present as an intranasal mass
- may extend into the upper pharynx
- neuroendocrine disturbances if the encephalocele is involves the sella turcica or sphenoid sinus

CLINICAL FEATURES:

1. Encephalocele

hernia may be a small CSF-filled meningeal sac or a large cyst-like structure that may exceed the size of the head - may be covered with skin and/or membrane of varying thickness - transillumination may show presence of neural tissue
may be pulsatile
covering may infarct and rupture -> infection

2. Complications (Neural)

Arnold-Chiari Malformation - Type 3
- an occipital encephalocele with a spina bifida over the cervical area with protrusion of the cerebellum through this opening
- may be associated with hydrocephalus
developmental delay
- i.e., motor with weakness and/or spasticity, ataxia
mental retardation
microcephaly
seizures
visual problems
- with occipital lobe involvement

INVESTIGATIONS:

1. Imaging Studies

1. Ultrasound

will determine the contents of the encephalocele
can detect encephaloceles in utero

2. CT/MRI

herniated brain tissue with a bony defect in the skull

2. Prenatal Diagnosis

elevated maternal serum alpha-feto-protein (AFP)
level II ultrasound
amniocentesis - elevated AFP and acetylcholinesterase

MANAGEMENT:

1. Surgery

correction is ineffective if the sac contains a significant amount of brain tissue
shunting required if hydrocephalus

2. Supportive

for complications
- physiotherapy
- anticonvulsants
- ophthalmology follow-up