Teaching Case

A 15-year-old girl had a history of recurrent seizures, progressive weakness of left upper limb and mental retardation since early childhood. She was born to non-consanguineous parents and had no history of any complications in the perinatal period. Past medical history was otherwise unremarkable and routine laboratory investigations were within normal limits.

Non-contrast CT scan of the brain revealed hemicerebral atrophy on the right side with diffuse sulcal enlargement and ex-vacuo enlargement of the right lateral ventricle. Mild midline structural shift was also present. The left cerebral hemisphere and the cerebellum appeared normal. Associated compensatory calvarial thickening and paranasal sinus hyperpneumatisation was noted on the affected side. These imaging findings and clinical history were consistent with Dyke-Davidoff-Mason syndrome.

Dyke-Davidoff-Masson syndrome (DDMS) is an uncommon clinical entity characterised by hemicerebral atrophy, contralateral hemiparesis, mental retardation and facial asymmetry. Hemicerebral atrophy is associated with compensatory hypertrophic changes in the calvarium, such as osseous thickening, hyperpneumatisation of the ipsilateral paranasal sinuses and mastoid cells and elevation of the petrous ridge. This entity was first described by Dyke, Davidoff, and Masson in 1993 on the basis of plain skull radiographic and pneumatoencephalographic changes in a series of 9 paediatric patients.

Although the exact aetiology is not well understood, both congenital and acquired causes have been postulated. Congenital DDMS is believed to be secondary to an in utero vascular insult principally in the middle cerebral artery territory. In the acquired variety, trauma, infection, vascular abnormalities and intracranial bleed have been implicated. This cerebral insult may occur either during the perinatal period or thereafter. Clinical symptoms vary depending upon the severity of cerebral insult. The most common presenting symptoms include intractable seizures, contralateral hemiparesis, mental retardation and learning disabilities. CT and MR imaging characteristically reveal focal or diffuse hemicerebral atrophy with ipsilateral osseous hypertrophy, hyperpneumatisation of the ipsilateral paranasal sinuses and mastoid air cells. These compensatory osseous changes may lead to cranio-facial asymmetry.

Differential diagnosis includes other conditions associated with cerebral hemiatrophy such as Sturge-Weber syndrome, Rasmussen's encaphlitis and Silver's syndrome. The hallmark anomaly in Sturge-Weber syndrome is a capillary malformation affecting the brain and meninges. Rasmussen’s encephalitis is a rare, chronic inflammatory neurological disorder typically affecting children under 10 years of age. It is also characterised by intractable seizures, hemiparesis and mental deterioration. At times, unilateral hemimegalencephaly as in the linear nevus sebaceous syndrome can be mistaken for DDMS. A meticulous and detailed clinical history is crucial for narrowing down the list of differentials.