Neonates suspected of having a degenerative disease but without family history or clinical signs suggestive of a particular degenerative disease should have their urine tested for sialic acid, glycoproteins, mucopolysaccharides, and N-acetylaspartate and arylsulfatase activity. Blood should be tested for very-long-chain fatty acids, N-acetylaspartate, copper, and ceruloplasmins, and an MRI of the brain should be performed. Enzyme studies in leukocytes and fibroblasts, and biopsies of nerve, muscle, skin, or liver should be done when a specific disease is suspected. There is no specific treatment for any of these disorders. The diagnosis of a degenerative disorder should be followed by genetic counseling.

Cerebellar lesions produce hypotonia with decreased or normal dynamic tone (Figure 115.1). Hypotonia and decreased or normal dynamic tone occur because damaged cerebellar neurons alter the alpha motor neurons indirectly by their influence on brain and brainstem structures.

Figure 115.1— Salient features of cerebellar hypotonia. Arrow indicates the site of dysfunction (cerebellum). US: brain ultrasound; CT: computerized tomography; MRI: magnetic resonance imaging.