NB. in a trauma context, spinal cord injury and other traumatic causes need to be considered
atraumatic weakness of the legs has a multitude of possible causes and it helps to determine the pattern of weakness:
if there is chest pain, abdominal pain or back pain, consider aortic dissection
are the arms involved
if so, it is unlikely to be a lower spinal cause
is it one leg with ipsilateral arm?
if so, it is likely to be a hemiplegic stroke (CVA)
if all four limbs are involved and patient is alert, consider a metabolic cause (check potassium, phosphate, calcium, TSH levels), spinal TIA, transverse myelitis, myositis (check CK), or other causes (see below)
is it bilateral and symmetric
does it spare sensory nerves and reflexes
cause is most likely at level of muscle or NM junction rather than at the spine
sporadic form mainly in the elderly -50 cases per million in those aged over 50 years
IBM2 hereditary form mainly in Iranian Jew ethnicity, presenting at age 20-40yrs with proximal leg weakness but sparing of quadriceps
uncommonly, an intracranial cause
single cause affecting only both legs is rare (eg. midline brain lesion), although normal pressure hydrocephalus tends to cause gait disturbance and incontinence
more common would be a multifocal process but then upper limb and /or face or other neurology would be expected
consider if other symptoms such as headaches, memory difficulties, etc.
if no eye features, but develops autonomic dysfunction within 3 months of onset, then consider Lambert-Eaton myasthenic syndrome (3 cases per million, and half will have an associated cancer, mostly small cell lung cancer)
other systemic conditions
paraneoplastic syndromes including paraneoplastic limbic encephalitis such as is associated with anti-Hu antibodies in association with small cell lung cancer
see below under ongoing weakness for more details - most spinal TIAs have a good recovery and no cause found and seem to only rarely develop a future spinal cord infarct
acutely impaired blood supply may result in an acute myelopathy with onset within minutes but may be a few hours in some cases
most patients have back or neck pain at the onset of symptoms and this is localized to the level of the lesion and ~ half were precipitated by movement which presumably compromised the blood supply to the cord 2)
some have a TIA-like presentation and most of these are cervical
some developed post-recovery hyperalgesia
most have a good recovery although those which arise following aortic surgery or involve the conus are more likely to have a poor recovery
no cause is found in most patients but other patients may have preceding prolonged hypotension or disc prolapse
rarely, it may be a form of intermittent claudication or arterial steal such as when there are recurrent attacks associated with an activity such as gardening
some other conditions as under sparing of arms
ED work up
history and exam with particular focus on discriminating findings as above such as UL vs LL, sensory vs motor, red flags of cauda equina syndrome (CES) or spinal infection, or a spinal “level” for a lesion
check post-void bladder scan
FWT urine
baseline bloods - FBE, U&E, LFTs, CRP, (CK if suspect myositis), (blood cultures if suspect infection)
urgent CT brain if:
stroke (CVA) or other intracranial cause seems likely (this is especially the case if ipsilateral arm and leg are involved)
NB. consider contrast scan if high risk of intracranial neoplasia or focal infection