A case of acute neurogenic weakness mimicking the axonal variant of the Guillain-Barre syndrome

An 86-year-old woman presented to the geriatric department with a 6-week history of low back and leg pains, which had started following an attack of diarrhoea and vomiting. She reported an aching sensation in her mid-thoracic region and pins and needles in her extremities. There was a history of Duke's B carcinoma of the colon, successfully excised in 1999, with no known recurrence. She lived alone and was independent. On examination in the Rapid Access Elderly Care unit, she was frail yet ambulant. There was global weakness, though particularly proximally, and she needed to use her arms to stand from a seated position. Reflexes were absent in the lower limbs and the plantar responses were flexor. There were no objective sensory deficits. General systemic examination was normal. The only routine blood test abnormalities were serum potassium of 2.2 mmol/l (3.5–5.3) and serum C reactive protein of 43.8 mg/l (0–10). MR scan of the thoraco–lumbar spine showed multilevel degenerative disc disease, worse at L4/5 and L5/S1. There was no compression of the spinal cord or nerve roots. ### Question 1 What is your impression of her presentation at this stage? Her clinical problem of back pain and aching is relatively common in an elderly care clinic, although her symptom onset was acute. The examination findings were also relatively non-specific at her age. Initial blood tests showed moderate hypokalaemia, which can be secondary to diarrhoea and can be associated with weakness, particularly in the elderly. The raised serum C reactive protein may have related to the diarrhoeal illness, but should probably be normal 6 weeks after an acute infection. The thoracolumbar spine imaging showed degenerative changes frequently seen in the elderly. ### Question 2 What would you do next? The geriatrician requested a nerve conduction study. This showed widespread reduction in amplitude of compound muscle action potentials, with only …