Classifying a novel brain malformation

Abstract

In this issue of Brain, Barth et al . present four case histories of children with a constellation of symptoms representative of a new brainstem malformation and associated syndrome, calling it ‘pontine tegmental cap dysplasia’ (PTCD: Barth et al ., 2007; p. 2258). This new malformation appears to be part of the ‘molar tooth’ family of brainstem anomalies, although with some unique characteristics that differentiate PTCD from inclusion in the Joubert spectrum of disorders for which the molar tooth sign has been considered a pathognomonic finding. Thus it is worth considering that PTCD may be a novel category within the classification of midbrain and hindbrain malformations, as recently proposed (Parisi and Dobyns, 2003; Table 1). View this table: Table 1 Classification scheme for malformations of mid-hindbrain development (adopted from Parisi and Dobyns, 2003) The four children profiled in the paper were unrelated to each other and none were the products of consanguineous unions. Their malformations were all discovered as part of routine referral to paediatric neurology. MRI performed on all four children revealed the molar tooth malformation, vermal hypoplasia, absent inferior olivary prominences, near-absence of the middle cerebral peduncles, flattening of the ventral pons and peaking of the pontine tegmentum (referred to as the ‘cap’ in the name for this malformation). Despite all four children having these findings, their neurological examination seemed to vary widely. Two were able to ambulate: three used sign language; and one had no purposeful movement and was severely delayed. All four children failed hearing tests, interpreted as indicating cranial nerve VIII involvement. There was variable involvement …