Encephalocele

Malformation characterized by cerebral anomalies and a median skull gap originating from the nasal root, orbits, or forehead (sincipital encephalocele), or the skull base or occiput (occipital encephalocele), allowing cerebrospinal fluid and/or brain to herniate. The encephalocele itself is defined as a herniation of part of the cranial contents through this skull defect. It may contain meninges (meningocele), meninges and brain (meningoencephalocele), or meninges, brain, and ventricle (meningoencephalocystocele).

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Cephalocele; Craniocele; Cranial Meningoencephalocele.

Defect of neural tube development resulting in a osseous defect in the midline of the skull that allows herniation of the meninges and portions of the brain.

1:5000-10,000 live births. No sexual predilection.

Multifactorial inheritance pattern.

Dysraphism of the skull with a defect that may occur anywhere from the nasal cavity to the foramen magnum. Herniation of cerebral structures with (encephalocystocele) or without ventricular components (cenencephalocele) are distinguished. If meningeal structures are involved in the herniation, the terms encephalomenigocele and meningoencephalocele have been used. Another classification distinguishes just between meningocele or encephalocele. The herniated brain is often abnormal, and there are frequently associated structural and functional abnormalities that also affect the nonherniated brain areas.

Based on the obvious clinical findings and confirmation by computed tomography scanning or magnetic resonance imaging. In utero diagnosis can be made by ultrasound, elevated maternal (and patient) alpha-fetoprotein, and amniocentesis.

The clinical picture depends on the type of encephalocele: Sincipital encephaloceles (25% of all encephaloceles) most often originate from the orbits, nose, or forehead and occur most commonly in Asians. (1) Anterior sincipital encephaloceles present as a mass in the nasopharynx. They are often diagnosed late and may present because of persistent nasal discharge or recurrent meningitis. (2) Basal sincipital encephaloceles may extend into the upper pharynx and present with feeding difficulties and/or upper airway obstruction. The content of the encephalocele may include hypothalamus or pituitary gland, which may result in neuroendocrine disturbances and preclude resection. The associated mortality is high.

Notencephaloceles (75% of all encephaloceles) extend from the occipital region aspect of the skull. Portions of the brain found in the herniated sac may include abnormal cerebral cortex, cerebellum, brainstem, and ventricles. There are often extensive malformations throughout the neuraxis with involvement of the midbrain, optic pathways, venous drainage, and skull. There may be a disturbance of the central autonomic control with abnormalities in temperature regulation. Seizures are common, and mental retardation is associated with extensive brain involvement. The hernia is usually covered with skin or membrane and may be pulsatile. The size may vary from a small sac to a cyst-like structure greater than the size of the head. Complications at presentation may include rupture of the sac with infection or necrosis. Associated neural abnormalities may include developmental delay, microcephaly, seizures, and mental retardation. Occipital encephaloceles may be associated with Arnold-Chiari Syndrome and hydrocephalus.

Several malformations have been identified to often coexist with encephaloceles, such as hydrocephalus, Klippel-Feil Syndrome (cervical vertebral synostosis and neck webbing), Arnold-Chiari Syndrome, porencephaly, agenesis of the corpus callosum, myelodysplasia, optic nerve dysplasia, and cleft lip/palate.

Coexisting syndromes and their associated anesthetic risks should be identified prior to anesthesia. Surgery may occur within the first 24 hours of life or may be delayed until after age 6 months depending on the location, size, and type of the encephalocele. Early complete surgical treatment is indicated to allow the developing brain and eyes to remodel the facial deformity. The goals of surgery include urgent closure of open skin defects to prevent infections and desiccation of brain tissue, removal or invagination of nonfunctional tissue, watertight closure of the dura, and total craniofacial reconstruction, particularly avoiding the “long-nose deformity.” To correct the deformity caused by hypertelorism and a long midface, Holmes et al. lower the supraorbital bar by rotating it medially, posteriorly, and downward in the midline, with lateral widening to correct the trigonocephalic deformity. Review computed tomography scans and/or magnetic resonance images if available before anesthesia.

These children may have difficult airway management secondary to the position of the encephalocele and associated abnormalities. Because subglottic stenosis has been reported in some patients, an endotracheal tube one size smaller than expected should be prepared as well. An anterior encephalocele may be associated with a large mass in the nasopharynx, so nasal tracheal intubation should be avoided. Supine positioning with a posterior encephalocele may be difficult even in the presence of bolsters to prevent external pressure on the encephalocele, so tracheal intubation should be performed in the (left) lateral position. Neonates have had their tracheas intubated awake in some cases. Maintenance of spontaneous ventilation is recommended until the airway has been secured if airway problems are expected. If there are any concerns regarding aspiration in combination with difficult airway management, a fiberoptic awake tracheal intubation is probably the technique of choice. Posterior encephaloceles are positioned prone, and nasal intubation using armored endotracheal tubes has been recommended as there are case reports of kinking or dislocation of the endotracheal tube that resulted in cardiac arrest. Changes in heart rate and/or rhythm may indicate brainstem compromise. Correct positioning of bolsters allows normal abdominal movement and venous flow in the inferior vena cava to reduce bleeding from the cerebral vessels and the vertebral venous plexus. Preparation for significant blood loss should be made because of potential bleeding from the suboccipital bone and dural sinus. Large-bore intravenous access is recommended, and invasive blood pressure monitoring with the possibility of drawing arterial blood gas samples (including complete blood count, hemoglobin, and coagulation parameters) should be considered. Maintenance of normal body temperature may be a problem because of brain exposure and significant volume replacement and may be complicated further by decreased central autonomic control. Use of forced-air warmers, heating blankets, warmed infusions, and other standard heating methods is recommended.

Use of atropine (0.02 mg/kg) prior to laryngoscopy and tracheal intubation has been recommended for all patients. Lumbar intrathecal morphine has been used for repair of frontal encephalocele via single-shot technique and provided effective analgesia for up to 24 hours.

Encephaloceles can be an isolated finding, but they may also be part of numerous syndromes, such as Acrocephalosyndactyly Syndromes, Median Cleft Facial Syndrome, Aplasia Cutis Congenita, Morning Glory Syndrome, Catlin Marks, MURCS Association, Cerebrorenodigital Syndrome, Pallister Hall Syndrome, Chondrodysplasia (giant cell type), Pentalogy of Cantrell, COACH Syndrome, Roberts Syndrome, Craniomicromelic Syndrome, Rolland Desbuqois Syndrome, HARD Syndrome, Smith-Lemli-Opitz Syndrome, Knobloch Syndrome, Streeter Anomaly, Krause Reese Syndrome, VACTERL Association (with hydrocephalus).