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Upper Motor Neurone Lesions
Definition: Lesions in the peripheral nervous system affecting neurons before their synapses in the anterior gray horn of the spinal cord or before their synapses in the ganglia of the cranial nerves.
Causes: This depends on the location and type of lesions. Types of lesions include traumatic, compressive, neoplastic and of degenerative nature. Examples of common sites are the spinal cord such as from tunours, intervertebral disk prolapses, stenosis, spondylolisthesis, cerebral infarctions and demyelinating diseases like multiple sclerosis.
Examination: Upper motor neuron lesions will produce: Increased tendon reflexes (hyperreflexia), muscle spasticity, particularly affecting the flexor muscles of the upper limbs and the extensor muscles of the lower limbs. Clasp-knife rigidity, an upgoing plantar response (Positive Babinski sign) and clonus. Superficial or cutaneous reflexes like cremasteric, anal and plantar may be absent.