EMG examinations performed on 32 children aged three to 13 years with ataxia-telangiectasia are reported from the Neurological Department of the Child Health Centre, Warsaw, Poland. Four main EMG patterns were distinguished: 1) normal, 2) increased polyphasia of motor unit potentials, 3) neurogenic lesions with denervation activity, 4) denervation, fasciculations, and a picture characteristic of advanced motor neuron disease. The severity of the neurogenic lesions increased from the proximal arm muscles to the distal leg muscles. An EVE pattern resembling motor neuron disease was seen most often in the extensor digitorum brevis. Nerve conduction studies showed a decrease in motor response amplitude in the older children and a reduction in sensory nerve action potentials in median and sural nerves of all children older than seven years. The authors consider that a generalized slowly progressive sensory system degeneration together with neurogenic amyotrophy affecting distal parts of the lower limbs is a constant feature of ataxia telangiectasia and can be taken to be one of the diagnostic characteristics. 
COMMENT. The clinical diagnosis of ataxia-telangiectasia is based on a progressive cerebellar ataxia, ocular telangiectasia, and inmuno logical abnormalities. Muscle weakness progresses with age and atrophy affects especially the distal leg muscles. The child is confined to a wheelchair after the 9th to the 12th year. EVE and nerve conduction studies are important in the diagnosis.