In the Gillespie syndrome, a combination of aniridia, cerebellar ataxia, and developmental delay is the denominating feature. In the Paine syndrome, a familial disorder with developmental delay, there is microcephaly, spasticity, optic hypoplasia, and myoclonic ataxia, the last presumably related to the cerebellar hypoplasia. These dysgeneses and the disequilibrium syndrome reported from Sweden are unified by the cerebellar ataxia; in the past, they were categorized as ataxic cerebral palsies. Imaging studies demonstrate the cerebellocerebral abnormality. Genetic factors are operative in some, but matters pertaining to etiology remain obscure (see the older monograph by Harding for details). One form of a pure nonprogressive congenital cerebellar hypoplasia has been mapped to a gene locus on chromosome Xq; it does not appear to be related to the fragile X syndrome, which may cause ataxia and tremor in adults as noted further on.
Differential diagnosis of the congenital ataxias The congenital ataxias must be distinguished from the progressive hereditary ataxias. The latter are likely to begin at a later age than the congenital ones. Some hereditary ataxias are intermittent or episodic, one of which is responsive to acetazolamide and is the result of an abnormality of the calcium channel as discussed in Chap. 5.
Also to be distinguished from the ataxias of congenital and neonatal origin is an acute cerebellar ataxia of childhood, which can usually be traced to a viral infection or postinfectious encephalitis, particularly after chickenpox. The opsoclonus-myoclonus (“dancing eyes”) syndrome of Kinsbourne is another postinfectious disease peculiar to childhood (see Chaps. 14 and 39). The cerebellar ataxia in this disease may be overshadowed by polymyoclonus, which mars every attempted movement. With improvement, under the influence of corticosteroids, a cerebellar disorder of speech and movement becomes evident. A majority of the patients in which the disease became chronic (16 of the 26 cases followed by Marshall et al) were found later to be cognitively impaired. The cause of the disease has never been established. An occult neuroblastoma or other tumor is uncovered occasionally. In the differential diagnosis of these acute forms of cerebellar ataxia, one must not overlook intoxication with phenytoin, barbiturates, or similar drugs.
The Flaccid Paralyses and the “Floppy Infant” (Table 37-7; See Also Chaps. 38 and 45)
The rare cerebral form of generalized flaccidity, first described by Foerster and called cerebral atonic diplegia, has already been alluded to in the discussion of cerebral palsy. It can usually be distinguished from the paralysis of spinal and peripheral nerve origin and congenital muscular dystrophy by the retention of postural reflexes (flexion of the legs at the knees and hips when the infant is lifted by the axillae), preservation of tendon reflexes, and coincident failure of mental development. The Prader-Willi syndrome, discussed earlier in the chapter, also presents at first as a generalized hypotonia.