Differential Diagnosis

A. Hydrocephalus. Occurs as a result of impaired production, flow, or absorption of cerebrospinal fluid (CSF) within the cranial vault. 1. Noncommunicating (obstructive) hydrocephalus. Caused by physical blockade of CSF flow from the ventricular system within the brain to the subarachnoid space surrounding the brain. This results in increased pressure within the intracranial space. Intracranial mass lesions (tumors, abscesses, vascular anomalies, and hamartomas) are often the cause of noncom-municating hydrocephalus. The most common cause in early infancy is aqueductal stenosis, which can be inherited or caused by infectious conditions and posthemorrhagic complications of prematurity. Other cerebral developmental disorders that can cause noncommunicating hydrocephalus include Dandy-Walker malformation, Chiari malformation, Klippel-Feil syndrome, and Warburg syndrome. 2. Communicating (nonobstructive) hydrocephalus. May occur following intracranial infection or hemorrhage, in addition to benign enlargement of subarachnoid space. Typically resolves by 2 years of age. A rare cause of hydrocephalus is overproduction of CSF by choroid plexus papilloma. Neurocutaneous Disorders. These disorders include cardinal features within CNS and skin. Several of these disorders may present with macrocephaly, including neurofibromatosis (the most common of these conditions) and tuberous sclerosis. Other neu-rocutaneous disorders include hypomelanosis of Ito, linear nevus sebaceous syndrome, and incontinentia pigmenti. Metabolic Disorders. Several metabolic disorders result in the storage of substances within the brain. These disorders include Alexander disease, Canavan disease, gangliosidoses, and mucopolysaccharidoses. Head circumference of a patient with one of these disorders typically is normal at birth but increases as the storage material builds up, causing child to regress neuro-logically.

Disorders of Skull Thickening. Disorders of bone that may result in thickening of the skull include rickets, osteogenesis imperfecta and hyperphosphatemia, to name a few. These disorders present as macrocephaly, without enlargement of CNS (brain). Familial Macrocephaly.

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