Assessment of the very young child with seizures is hampered by the very limited repertoire of which the nervous system is capable. Nevertheless, one can acquire a good estimate of the child’s capabilities by observing his or her level of alertness and interaction with the surroundings and the child’s vocalization, feeding habits, motor activity, and muscle tone. Severe hypotonia at birth and progressive spasticity are common to many neurodegenerative diseases.

Vision loss

Vision loss accompanies several neurodegenerative diseases, including:

  • leukodystrophies (e.g., Krabbe’s disease and Canavan’s disease)
  • neuronal storage diseases (e.g., GM1 and GM2 gangliosidoses, sialidosis type I, and the neuronal ceroid-lipofuscinoses)

Findings in the retina may include:

  • optic atrophy
    • leukodystrophies
    • Menkes’ syndrome
  • cherry-red macula
    • gangliosidoses
    • sialidosis type I
  • retinal pigmentary degeneration
    • Cockayne’s syndrome
    • neuronal ceroid-lipofuscinoses
    • mitochondrial encephalopathies

Cortical blindness as an early sign prompts consideration of adrenoleukodystrophy or juvenile globoid cell leukodystrophy and often is part of the clinical picture of MELAS.

Disturbances in ocular motility with gaze initiation failure occur in type 2 Gaucher’s disease and Niemann-Pick disease type C. Supranuclear palsies of conjugate gaze are also a feature of Leigh disease and Huntington’s disease.

Movement disorders

Cerebellar ataxia may be noted after the child begins to reach for objects, to sit, and to stand. It may be progressive, as in the sphingolipidoses and in cerebrotendinous xanthomatosis, or episodic, as in the aminoacidopathies and organic acidopathies.

Useful extrapyramidal signs of metabolic disease include:

  • rigidity
  • dystonia
  • chorea
  • bradykinesia
  • athetosis
  • tremor

Among the metabolic diseases that should be considered when these signs occur are:

  • Wilson’s disease
  • juvenile Huntington’s disease
  • dentatorubral-pallidoluysian atrophy
  • glutaric aciduria type I

Peripheral neuropathy

The involvement of peripheral nerves can assist in making a diagnosis of neurometabolic disease:

  • demyelinating neuropathy
    • Krabbe’s disease
    • metachromatic leukodystrophy
    • Cockayne’s syndrome
  • axonal neuropathy
    • Schindler’s disease
    • Lowe syndrome

A peripheral neuropathy may also occur in:

  • some mitochondrial disorders
  • Sanfilippo’s syndrome
  • neonatal adrenoleukodystrophy

Adapted from: Kolodny, EH. Metabolic and genetic disorders. In: Devinsky O and Westbrook LE, eds. Epilepsy and Developmental Disabilities. Boston: Butterworth-Heinemann; 2001;17–22. 
With permission from Elsevier (www.elsevier.com). 

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