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ABNORMALITIES OF HEAD SIZE

ABNORMALITIES OF HEAD SIZE

(MACROCEPHALY & MICROCEPHALY)

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MICROCEPHALY• Literarily means “Small Head”• Defined as occipito-frontal

circumference less than the 5th centile for age OR more than 2SD below the mean for the age.

• Microcephaly may be subdivided into two main groups: primary (genetic) microcephaly and secondary (nongenetic) microcephaly.

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• Primary microcephaly refers to a group of conditions that usually have no other malformations and follow a mendelian pattern of inheritance or are associated with a specific genetic syndrome.

• The more common types include familial and autosomal dominant microcephaly and a series of chromosomal syndromes.

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• Secondary microcephaly results from a large number of noxious agents that may affect a fetus in - utero or an infant during periods of rapid brain growth, particularly the first 2yr of life.

• These are common in this environment than the primary types.

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SECONDARY MICROCEPHALY

• Izuora (Enugu, 1987) Asphyxia neonatorum (with ICH) Severe neonatal jaundice Repeated early neonatal convulsions Prematurity TORCHES infection Neonatal tetanus with recurrent apnea• Others include: Meningitis/encephalitis Maternal phenylketonuria Drugs (alcohol, phenytoin) Irradiation

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SYNDROMES ASSOCIATED WITH

PRIMARY MICROCEPHALY

• Down (21-trisomy)

• Edward (18-trisomy)

• Cri-du-chat (5 p-)

• Cornelia de Lange

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DIAGNOSISSkull radiograph, CT scan/MRI to

detect calcifications and cerebral atrophy.

Serology: To screen for the TORCHES infection using antibody titres.

Maternal serum phenylalanine.Karyotype for chromosomal

analysis. Fasting plasma/ urine amino acid

analysis.

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CRANIOSYNOSTOSIS (CRANIOSTENOSIS)

• Craniosynostosis is defined as premature closure of the cranial sutures due to abnormalities of skull development.

• The cause is unknown. • Genetic syndromes account for

10–20% of cases. • The most prevalent genetic

disorders associated with craniosynostosis include (1) Crouzon (2) Apert (3) Carpenter syndromes.

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FONTANELLES & SUTURES

• FONTANELLEAnteriorPosterior• SUTURESSagittalCoronalLambdoidMetopic

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FORMS OF CRANIOSYNOSTOSIS

• Scaphocephaly (boat-shaped) corresponding to sagittal synostosis.

• Plagiocephaly (oblique or sloping) corresponding to unilateral coronal synostosis.

• Trigonocephaly (triangular-shaped) corresponding to metopic synostosis.

• Brachycephaly (short head; both coronal sutures)

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CLINICAL MANIFESTATION

• Most cases of craniosynostosis are evident at birth.

• Characterized by a skull deformity that is a direct result of premature suture fusion.

• Palpation of the suture reveals a prominent bony ridge.

• Fusion of the suture may be confirmed by plain skull roentgenograms or bone scan in ambiguous cases.

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CLINICAL MANIFESTATIONS

• Syndromic types are also associated with airway problems from maxillary hypoplasia.

• Difficulty with nose-breathing may occur, hence, mouth-breathing is common.

• Sleep apnea affects not only their growth pattern, but also their behavior and speech.

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CLINICAL MANIFESTATIONS

• Children with raised intracranial pressure (ICP) can complain of chronic headaches, declining school performance, and gradual visual failure.

• As children grow, abnormal facial appearance has a negative effect on their social integration, with a corresponding effect on personality development.

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CLINICAL MANIFESTATIONS

• Progressive facial and cranial deformity, intracranial hypertension, and progressive exophthalmos threatening the eyes.

• Increased ICP, papilledema, optic atrophy due to abnormalities of the optic foramina, respiratory problems secondary to a deviated nasal septum or choanal atresia, and disorders of speech and deafness.

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MANAGEMENT• Plain radiographs (abnormal

sutural ridging)• CT scan/MRI (to exclude cortical

atrophy)• Craniectomy

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MACROCEPHALY• Literarily means “Big Head”• Defined as occipito-frontal

circumference more than the 95th centile for age OR more than 2SD above the mean for the age.

• It may be a variant of the normal (constitutional or familial) or abnormal (due to enlarged skull, enlarged brain or accumulated fluid within the cranium).

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CAUSES OF MACROCEPHALY

• Enlarged skullRicketsHaemoglobinopathies (SCA,

Thalassaemia)Achondroplasia• Accumulated fluidIntraventricular (Hydrocephalus)Subdural effusions/ haematoma/

empyema

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CAUSES OF MACROCEPHALY

• Enlarged brain tissuesNeurofibromatosisCerebral gigantismMaple syrup urine diseaseDegenerative diseases like

glycogen storage diseasesBrain tumors

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HYDROCEPHALUS• Abnormal enlargement of the head as a result

of CSF accumulation and ventricular dilatation.

• The CSF is formed primarily in the ventricular system by the choroid plexus, which is situated in the lateral, third, and fourth ventricles. Stimulation of the adrenergic system diminishes CSF production, whereas excitation of the cholinergic nerves may double the normal CSF production rate.

• In a normal child, approximately 20 mL of CSF is produced per hour. The total volume of CSF approximates 50 mL in an infant and 150 mL in an adult. Most of the CSF is extraventricular i.e in the subarachnoid space.

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PATHOPHYSIOLOGY• Normally, CSF flows from the

lateral ventricles through the foramina of Monro into the third ventricle. It then traverses the narrow aqueduct of Sylvius to enter the fourth ventricle. The CSF exits the fourth ventricle through the paired lateral foramina of Luschka and the midline foramen of Magendie into the cisterns at the base of the brain.

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PATHOPHYSIOLOGY• Hydrocephalus resulting from

obstruction within the ventricular system is called obstructive or noncommunicating hydrocephalus.

• Hydrocephalus resulting from the obliteration of the subarachnoid cisterns or malfuncion of the arachnoid villi is called nonobstructive or communicating hydrocephalus.

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AETIOLOGY• Congenital Aqueductal stenosis Vein of Galen malformation (obstructing CSF

flow) Posterior fossa malformations (Dandy-Walker,

Chiari)• Acquired Meningitis (pyogenic & tuberculous) Intracranial (intraventricular) haemorrhage TORCHES infection Leukaemic infiltrates

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CLINICAL MANIFESTATIONS

In an infant, an accelerated rate of enlargement of the head is the most prominent sign.

The anterior fontanel is wide open and bulging.

The scalp veins are dilated and prominent.

Cranio-facial disproportion (broad forehead dwarfing the face)

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CLINICAL MANIFESTATIONS

Setting-sun eye appearance (from impingement of the dilated suprapineal recess on the tectum)

Sutural diastasis (widely separated sutures)

“Cracked pot” note on percussion of the skull (Macewen sign).

A foreshortened occiput suggests Chiari malformation, and a prominent occiput suggests the Dandy-Walker malformation.

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CLINICAL FEATURES• In an older child, the cranial sutures are

partially closed so the signs may be more subtle (Irritability, lethargy, poor appetite, and vomiting)

• Papilledema, CN VI palsy, and pyramidal tract signs, which are most evident in the lower extremities, are apparent in most cases.

• Brisk tendon reflexes, spasticity, clonus and Babinski sign occur owing to stretching and disruption of the corticospinal fibers

• Spinal bifida may occur in Dandy Walker malformation.

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DIAGNOSIS• Clinical features.• Transillumination.• Skull radiography to verify

chronically raised intracranial pressure.

• Transfontanelle ultrasound/ CT scan/MRI which show ventricular enlargement with fluid accumulation.

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MANAGEMENT• MEDICALUse of drugs like Acetazolamide

(5mg/kg/dose q 8 hourly) and Frusemide (1-2mg/kg/dose q 12 hourly) which reduces CSF production

• SURGICALExtra-cranial shunts (Ventriculo-atrial

shunts and ventriculo-peritoneal shunts)

Major problems of the shunt procedures are recurrent infections (meningitis), kinking and need to review the length with increasing age and growth.