Table 2.

Summary of Neurologic Studies

Subject	Age	Motor Exam	Sensory Exam	Reflexes	Cerebellar Exam	Neuropsychiatric Evaluation	Nerve Conduction Studies*	T8993C Mutant Heteroplasmy† in Blood; Hair
I-1	48	Moderate proximal muscle weakness and superimposed right sided pyramidal weakness	Prolonged vibratory thresholds, decreased pain sensation on right side of body	Absent triceps and ankle reflexes with no response on Babinski testing	Normal	Depression and visuospatial deficits	Mild length-dependent sensorimotor neuropathy	78; 87
II-1	28	Moderate proximal muscle weakness, subtle lower extremity spasticity	Sensory drift, prolonged vibratory thresholds in right arm, absent ankle reflexes	Brisk at knees, absent ankle reflexes	Limb ataxia	Depression	Moderate length- dependent sensory neuropathy	78; 99
II-2	26	Normal	Normal	Normal	Normal	Prior depression, slow visuospatial processing, low normal planning/ executive function	Not tested	42; 54
II-3	22	Proximal muscle weakness with superimposed pyramidal weakness especially in the lower extremities with spasticity	Prolonged vibratory thresholds, decreased pain sensation in left hand and foot	Very brisk at triceps and knees (left greater than right) and absent at ankles	Limb and truncal ataxia, sustained end gaze nystagmus and overshoot saccades, cerebellar dysarthria	Depression, poor attention, disinhibition, severely impaired visuospatial memory and verbal fluency	Moderate length- dependent sensorimotor axonal poly-neuropathy (upper and lower extremities)	95; 99
II-4	16	Mild proximal muscle weakness, lingual dysarthria	Prolonged vibratory thresholds	Reduced ankle reflexes	Limb ataxia	Impaired visuospatial memory and verbal recall	Moderate length- dependent sensorimotor axonal neuropathy (lower extremities)	92; 99

Pyramidal weakness, injury to descending motor inputs from the central nervous system; dysarthria, impairment of speech.

^*Nerve conduction studies include techniques for assessing electrophysiologic evidence of peripheral nerve dysfunction.

^†The degree of T8993C mutant heteroplasmy is expressed as percent of total mitochondrial DNA.