5) DEGENERATIVE DISEASES - FRIEDREICH'S ATAXIA
A Sample Case:A 15 year old boy was referred to a neurologist when he complained of difficulty in running and developed a staggering gait, poor articulation in speech and clumsiness in the hands during an 8 month period. These symptoms were recalled to be like that of his uncle who became similarly disabled in his early 20's and confined to a wheelchair before finally becoming bedridden.
The physical examination revealed an unsteady, broad-based stance and sudden lurching when walking which was accompanied by a "slapping" sound made by the feet. Loss of vibratory and position sense was observed bilaterally in all extremities. There was a tremor of the upper extremity as the patient reached for objects. Speech was slurred, slow and with an uneven pattern. Hyporeflexia was present but there was only a slight indication of muscle atrophy though there were bilateral Babinski signs.
The findings of the exam indicate an ataxia of the sensory as well as cerebellar type; there are also indications of corticospinal tract disease. The broad-based, unsteady stance and gait are consistent with posterior white column disease as well as cerebellar disease. Slapping of the feet, to auditorily supplement sensory feedback, is consistent with patients deprived of conscious proprioception. Decreased or abolished tendon reflexes is usual with sensory deprivation due to degeneration of the dorsal roots, as occurs with posterior white column degeneration. Intention tremor and slurred speech is characteristic of patients with cerebellar disease.
Positive Babinski signs indicate involvement of the corticospinal tracts. In this disorder there is usually a foot deformity called pes cavus in which there is hypertonia resulting in a high plantar arch with retraction of the toes at the metatarsal-phalangeal joints.
Pathologic examination of the cord in Friedreich's ataxia indicate a small cord with degeneration in the posterior white columns, corticospinal and posterior spinocerebellar tracts. The motor cortex and cerebellum also show loss of cells. This is a hereditary progressive ataxia. About half the cases appear before the age of 10 and within 5 years of onset walking is no longer possible. There are two patterns of inheritance, one dominant the other recessive. Males are somewhat more susceptible.