Somatosensory Evoked Potentials in Hallervorden-Spatz-Neuroaxonal-Dystrophy Complex with Dorsal Column Involvement

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Abstract
Two patients with a marked hypointensity of the globus pallidus on magnetic resonance imaging (MRI), which is known to be diagnostic for Hallervorden-Spatz disease (HSD), are presented. Patient 1 fell ill at about 10 years of age with visual disturbance, spastic paraplegia and mild ataxia, while patient 2 was affected during the second year of life with clinical features compatible with infantile neuroaxonal dystrophy (INAD). The two patients had certain clinical features in common; upper and lower motor neuron involvement, visual disturbance secondary to optic nerve atrophy, and dorsal column dysfunction, the evidence of which was seen from abnormal somatosensory evoked potentials (SEPs) obtained after posterior tibila nerve stimulation. In both patients, electron microscopic examination of the biopsied skin or sural nerve showed dystrophic axons, spheroids, and involvement of the peripheral nerve was indicated. Sharing of these clinical, pathological and MRI characteristics by the two patients supports the view of Seitelberger, who regarded HSD and INAD as constituents of a single disease entity, therefore the two patients were described as belonging to a disease spectrum of "Hallervorden-Spatz-neuroaxonal-dystrophy complex (HS-ND)." Sensory impairment has been a rare clinical feature in "HS-ND" complex, although its existence is not inconceivable considering the usual affection of the dorsal column/lemniscal pathway with spheroids. SEP was considered very useful in disclosing this often unmanifested sensory disturbance in "HS-ND" complex.