Upper Motor Neuron Weakness
June 30th, 2019
Overview
Signs of Upper Motor Neuron Weakness
- Minimal muscle wasting
- Spasticity (clasp-knife rigidity) - velocity-dependent increase in tone
- Clonus - rhythmic contractions in response to a sudden stimulus, e.g. sudden ankle dorsiflexion
- Reduced power
- Hyperreflexia
- Upgoing plantar reflex
Significance
- The presence of upper motor neuron weakness suggests a lesion within the central nervous system, involving the cerebrum, brainstem or spinal cord.
Causes of Upper Motor Neuron Weakness
- Ischaemia - ischaemic stroke, spinal cord infart
- Haemorrhage - subarachnoid haemorrhage, intracerebral haemorrhage
- Traumatic brain injury
- Tumour - astrocytoma, meningioma, brain metastases, spinal cord neoplasia
- Infection - encephalitis, PML, brain abscess
- Demyelination - ADEM, multiple sclerosis
- Hereditary spastic paraparesis
- Idiopathic transverse myelitis
- CNS vasculitis
- Sarcoidosis
- Syringomyelia
- Prion disease
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