A woman with rapidly progressive weakness and sensory loss

A 61 year old woman presented to the accident and emergency department with progressive weakness of the lower limbs and a feeling of her legs being “frozen” over the preceding four days. Ten days earlier, she had contracted a flu-like illness and was diagnosed and treated with oseltamivir (Tamiflu) for presumed swine flu. She was later found to be influenza A/H1N1 seropositive on the reference laboratory haemagglutination assay. Her medical history included cervical spondylosis for which she had decompressive laminectomy (C4-7) in 1992 and a Cloward’s discectomy with bone graft and fusion of C5-7 in 1996.

On examination she had a score of 15 on the Glasgow coma scale and was afebrile, with normal pulse and blood pressure. She had an ataxic gait and could not walk unaided. She also had Medical Research Council grade 3/5 symmetrical weakness of the lower limbs, in addition to absence of leg reflexes and flexor plantars. Sensation was reduced over her left thigh. Her left arm was weak in the triceps and biceps, grade 3/5; thumb abduction was reduced bilaterally, grade 4/5; left triceps and right supinator reflexes were absent. Cranial nerves and the rest of the neurological examination were normal.

Magnetic resonance imaging of the cervical spine showed degenerative changes that caused narrowing of the spinal canal between C5 and C7 but did not affect the spinal cord or nerve roots; in addition no intrinsic spinal cord abnormality was seen. Magnetic resonance imaging of the brain was normal. The cerebrospinal fluid contained 1 g protein/L (reference range 0-0.5) and 22×10⁶ white blood cells/L (0-5×10⁶) (85% lymphocytes, 15% polymorphs).