When myasthenia gravis is not all.

Weakness of the extrinsic ocular muscles (EOM), resulting in fluctuating ptosis and diplopia, is very frequent in myasthenia gravis (MG). Therefore, in patients with an established diagnosis of MG, the onset/worsening of ocular complaints is commonly related to the disease. We hereinafter report two patients whose ocular disturbances were not all justified by MG. Case 1 A 76-year-old woman presented with diplopia and left ptosis. Clinical examination revealed loss of function of left inferior and medial recti muscles, confirmed on Hess screen. Ptosis improved on neostigmine test, and anti-acetylcholine receptor antibodies (AChR Abs) were positive (3.81 nM/l; normal range \0.45). Thyroid function and auto-Abs were normal. The patient was diagnosed with ocular MG and was given prednisone (25 mg/day), with regression of both ptosis and diplopia within three weeks. During steroid tapering she developed vertical strabismus due to non-fluctuating, complete palsy of the left inferior rectus muscle; oral prednisone was gradually increased up to 50 mg/day with no benefit. In this stage neostigmine test was negative; thyroid function and auto-Abs remained within normal limits. After a 3-month treatment with 50 mg/day prednisone, the patient underwent brain/orbital magnetic resonance imaging (MRI) with gadolinium, revealing altered signal, swelling, and contrast enhancement of her left inferior rectus muscle, suggesting myositis (Fig. 1a). Methylprednisolone pulse therapy (1,000 mg e.v./day for five consecutive days), followed by oral prednisone on alternate days was administered, with rapid improvement and complete symptom resolution within three months. One year later, a second brain MRI showed a regression of myositis with minimal thinning of the inferior rectus muscle (Fig. 1b). The final diagnosis, in this case, was of ocular MG associated with orbital myositis. Case 2 A 62-year-old woman reported a two-month history of left ptosis, diplopia on the left lateral gaze, and limb fatigability. Brain MRI with gadolinium was negative. Generalized MG was diagnosed on the basis of clinical signs, decremental response on repetitive nerve stimulation, abnormal jitter on single-fiber EMG, and serum AChR Abs detection (2.50 mM/l). Treatment with pyridostigmine resulted in marked improvement of ptosis and limb weakness, whereas diplopia limited to the left lateral gaze remained unaffected. At the following visit six months later, the patient showed pseudo-internuclear ophthalmoplegia. Steroid treatment with prednisone (25 mg/day, for two months) was not effective; thus, dosage was increased up to 50 mg/day, and was maintained steadily for three months with no change in pseudo-internuclear ophthalmoplegia. Thyroid function and auto-Abs were normal on repeated assays. Brain/orbital MRI with gadolinium showed a severe atrophy of the left lateral rectus (Fig. 1c, d). The final diagnosis was generalized MG associated with early EOM atrophy. After three months, a further MRI confirmed these findings, and the patient opted for eye muscle surgery. Prednisone dosage was gradually reduced V. Damato (&) P. E. Alboini A. Mastrorosa A. Evoli Institute of Neurology, Catholic University, Largo A. Gemelli 8, 00168 Rome, Italy e-mail: valedamato@hotmail.com