Progressive impairment of cognition and motor function: Hashimoto encephalopathy.

emergency department with a de creased level of consciousness after having had a generalized tonic–clonic seizure for the first time. Her score on the Glasgow Coma Scale was 8. Her vital signs were stable, and her blood glucose was normal. Mechanical ventilation was started. A computed tomography scan of her head showed no evidence of intracranial bleeding or space-occupying lesions. No other abnormalities could be seen. She was admitted to the intensive care unit. The patient’s medical history included gastro esophageal reflux disease. She did not take any medications regularly, and she had no known allergies. Her family history included a maternal grandmother with hypothyroidism. According to her family, the patient lived independently, worked at a job requiring high cognitive function, had a 40 pack-year history of smoking, drank minimal amounts of alcohol socially and did not use illicit drugs. Over the past year, she had been seeing a neurologist for progressive confusion and unsteadiness. Recent falls had caused her to start using a walker. The neurologist had noted some features in her presentation that were consistent with Parkinson disease: bradykinesia, mask-like facies, vague and slow responses to all general questioning, some resting tremor of her left hand, cogwheel rigidity and difficulty tapping her left foot. Magnetic resonance imaging of her brain and cervical spine had not shown demyelination, atrophy or changes in the basal ganglia. An electroencephalogram had shown slow and poorly reactive background activity. The neurologist had started a trial of ropenirole (a dopamine agonist), but the patient’s symptoms had worsened. Although she was subsequently given sinemet (carbidopa –levodopa), no significant improvement was noted in either her tremor or her bradykinesia. She had recently been referred to the regional movement disorder clinic with a possible diagnosis of young-onset Parkinson disease. During her stay in the intensive care unit, the patient’s level of consciousness improved spontaneously, and mechanical ventilation was stopped. However, she remained confused and was not oriented to time, person or place. The only abnormality detected by initial laboratory tests was an elevated level of thyroid -stimulating hormone (14 [normal 0.5–5.0] mIU/L); her levels of free triiodothyronine and thyroxine were normal. The patient’s cerebrospinal fluid was unremarkable, except for an elevated level of protein (1.21 [normal 0.15–0.45] g/L). No growth was seen in a culture of her cerebrospinal fluid. We considered Hashimoto encephalopathy because of the patient’s progressive confusion and unsteadiness and her elevated level of thyroidstimulating hormone. She was given high doses of steroids (prednisone, 100 mg daily), and her confusion diminished within 24 hours of starting treatment. She was discharged with home care support one week later. Laboratory tests later showed that the patient had extremely elevated levels of antibodies against thyroglobulin (24300 IU/L, normal < 40 IU/L) and thyroid peroxidase (3056 IU/L, normal < 40 IU/L). Over the next few months, the patient continued the steroid treatment (prednisone, 50 mg daily) and showed marked improvement in her steadiness. Her cognition also improved, and she contemplated returning to work. Laboratory investigations showed a decrease in her titres of antibodies against thyro globulin (5400 IU/L) and thyroid peroxidase (440 IU/mL). Cases