A 44-year-old, right-handed woman presented with a 2 year history of intermittent burning and numbness over the left side of her face which had become continuous for the past 9 months. Over the past 7 months she had experienced spasms characterised by a sensation that the left side of her mouth was being pulled tight, associated with spontaneous flexed posturing of the left elbow and wrist with clawing of the hand. The spasms lasted for approximately 15 s and were extremely painful. They occurred in paroxysms lasting up to 2 h, several times a week.

One month prior to presentation, she developed double vision on looking to the left with vertical separation of the images, and vertigo. She also reported fatigue, dry mouth and dry eyes over the previous 2 years. There was no previous medical history and she was taking no medications. Family history was unremarkable.

Examination showed a markedly dry mouth. There was no skin rash or joint inflammation. On left lateral gaze the left eye deviated upwards in comparison with the right, a left hypertropia. Eye movements were otherwise normal. There was subjective reduction in sensation over the left side of the face in all trigeminal nerve divisions, consistent with a sensory trigeminal neuropathy, with preservation of the corneal reflex. Neurological examination was otherwise unremarkable.

Routine biochemistry and haematology were normal. P and C antineutrophil cytoplasmic antibodies, rheumatoid factor, tissue autoantibodies, extractable nuclear antigen antibodies, anti-scl-70, anticentromere, antiphospholipid, anti-Jo1, anti-Ro, anti-La, anti-RNP and anti-Sm antibodies were all consistently negative. Antinuclear antibodies were slightly raised at a titre of 1 in 40 but double stranded DNA antibodies were negative.

MRI of brain and cervical spine with contrast was normal. Lumbar puncture showed normal opening pressure, protein, glucose and cell count, and was negative for oligoclonal bands. Chest x …