Paraplegia is a total weakness (paralysis) of the lower limbs (cf. paraparesis). This may result from lower motor neurone lesions involving multiple nerve roots and/or peripheral nerves (e.g., paraparetic GuillainBarré syndrome) producing a flaccid, areflexic paraplegia; but more commonly it is due to upper motor neurone lesions interrupting corticospinal pathways (corticospinal tract, vestibulospinal tract, reticulospinal tracts, and other extrapyramidal pathways), most usually in the spinal cord. The latter may acutely produce a flaccid areflexic picture ("spinal shock"), but later this develops into an upper motor neurone syndrome (hypertonia, clonus, hyperreflexia, loss of superficial reflexes [e.g., abdominal, cremasteric reflexes] and Babinski’s sign) with possible lower motor neurone signs at the level of the lesion; bladder involvement is common (urinary retention). Because of the difficulty in distinguishing whether an acute paraplegia is of LMN or UMN origin, imaging to exclude potentially reversible cord compression is mandatory.
Recognized causes of paraplegia of upper motor neurone origin include:
- Traumatic section of the cord
- Cord compression
- Inflammatory lesions: acute transverse myelitis of viral origin, multiple sclerosis, neuromyelitis optica (Devic’s syndrome)
- Ischemic lesions; anterior spinal artery syndrome, venous infarc- tion of the cord.
In paraplegia of upper motor neurone origin, enhanced flexion defense reflexes ("flexor spasms") may occur, producing hip and knee flexion, ankle and toe dorsiflexion. Eventually such flexor responses may become a fixed flexion deformity with secondary contractures ("paraplegia in flexion"). Prevention of this situation may be possible by avoiding spasms, which are often provoked by skin irritation or ulceration, bowel constipation, bladder infection, and poor nutrition. Physiotherapy and pharmacotherapy with agents, such as baclofen,
dantrolene, and tizanidine may be used; botulinum toxin injections may be helpful for focal spasticity.
"Paraplegia in extension", with extension at the hip and knee, may be seen with incomplete or high spinal cord lesions.
Johnston RA. Acute spinal cord compression. In: Hughes RAC (ed.). Neurological Emergencies (2nd edition). London: BMJ Publishing, 1997: 272-294
Passmore AP, Taylor IC, McConnell JG. Acute Guillain-Barré syndrome presenting as acute spinal cord compression in an elderly woman. Journal of the Royal Society of Medicine 1990; 83: 333-334
Abdominal reflexes; Areflexia; Babinski’s sign (1); Clonus; Contracture; Cremasteric reflex; Flaccidity; Hyperreflexia; Hypertonia, Hypertonus; Lower motor neurone (LMN) syndrome; Myelopathy; Paraparesis; Spasticity; Upper motor neurone (UMN) syndrome; Urinary retention