Spasms and Myoclonus in a Young Woman With Hashimoto Thyroid
A 39-year-old woman presented to the emergency department with a 3-week history of worsening spasms in her axial and lower limb muscles and new-onset urinary retention. Sudden episodes of painful involuntary spasms first appeared in her abdominal muscles 2 weeks after a cold. Soon after, spasms spread to all of her axial muscles and both lower limbs. These paroxysmal episodes lasted a few seconds, occurred up to 20 times a day, and were exacerbated by external stimuli. There was no impairment of consciousness during the attacks. A review of her previous records revealed a diagnosis of Hashimoto thyroiditis 1 month earlier. She had hyperhidrosis and tachypnea on admission. Neurological examination results disclosed an abnormal mental status. Cranial nerve examination results demonstrated slow saccades. Motor system examination results revealed asymmetric and severe hypertonia and rigidity throughout her trunk and all 4 extremities.

Further notable occurrences were severe spasms and patella clonus associated with brisk deep tendon reflexes. She demonstrated marked myoclonus on tactile and acoustic stimulation. Extensor plantar responses were present bilaterally. Laboratory results were significant for an elevated level of thyroperoxidase antibodies (50.85 IU/mL; normal,<5.16IU/mL) and thyroglobulin antibodies (88.35 ng/mL; normal:<4.11 ng/mL; to convert to micrograms per liter, multiply by 1). Cerebrospinal fluid testing results revealed normal protein level and cell counts, as well as absent oligoclonal bands or evidence of infection. Needle electromyography (EMG) results showed continuous firing of normal motor unit potentials at rest within the axial and lower limb muscles. A routine electroencephalogram (EEG) showed mild background slowing without periodic discharges. Computed tomography scan results of the thorax, abdomen, and pelvis were negative. An electrocardiogram showed sinus tachycardia. The patient’s severe clinical features included rigidity and painful spasms as well as persistent myoclonus that was associated with typical EMG features. These findings are highly suggestive of Progressive encephalomyelitis with rigidity and myoclonus.

Management of PERM is focused on immunotherapy, symptomatic treatment, and tumor screening and treatment.9 Prognosis is highly variable among patients; patients with GAD65 antibodies generally had a worse prognosis than patients with GlyR antibodies.5 Continuous monitoring and maintenance therapy are important as PERM typically has a high likelihood of relapse and residual disability. The patient was treated with intravenous immunoglobulin (0.4 g/kg/d) for 5 days, intravenous methylprednisolone (500mg/d) for 5 days with an oral prednisone taper, and intravenous diazepam (60 mg/d) for 5 days followed by a taper within 3 weeks. Oral clonazepam (6 mg/d) was used as maintenance therapy. On a 6-month follow-up, she demonstrated marked improvement with undetectable serum GAD antibodies. There was no evidence of malignancy over the 1-year follow-up.