“Ms. A,” age 26, presented with a 2-year illness with episodic exacerbations characterized by pervasive irritability, overactivity, and overtalkativenesss, associated with poor occupational functioning and partial response to valproate, quetiapine, and olanzapine. For 2 years after the onset of mood symptoms, Ms. A had episodes of abrupt-onset, generalized weakness of all limbs, lasting for 30 minutes, with spontaneous resolution and no associated loss of consciousness. These episodes of weakness were present during the exacerbation of affective symptoms. Family history was not contributory. The patient had a history of low birth weight, mild delay in milestones, and poor scholastic performance. On physical examination, she had anomalies that included hypertelorism; flat nasal bridge; low-set ears; ill-formed auricular cartilage, with adherent ears; high arched palate; micrognathia; clinodactyly; and short stature. During her hospital stay, Ms. A had two episodes characterized by abrupt-onset, generalized hypotonia; grade 2 power in all limbs, with absent reflexes; bilateral flexor-plantar response, and normal sensorium. Both episodes lasted for less than 1 hour, and the second episode improved after potassium supplementation. Mental status examination during the inpatient stay revealed increased psychomotor activity, increased speech output, pervasive irritable mood, and impaired concentration, with no delusions or hallucinations. Serum potassium level level during the first episode of weakness was not available; however, during the second episode, it was 5.1 meq/liter. Serum magnesium, calcium, renal and liver function tests, and thyroid profile were within normal limits, and urine for myoglobin was negative. ECG interval was normal (QTc: 0.36 seconds), and there were no ventricular ectopics. The brain MRI was within normal limits. IQ testing revealed an IQ of 57.
The patient was diagnosed with bipolar affective disorder with current episode mania without psychotic symptoms (ICD-10). The impression was periodic paralysis, with which the neurology team in the hospital concurred. She was started on olanzapine 20 mg, to which there was partial response. Lithium carbonate was added, at 900 mg, and increased to 1,050 mg to reach an adequate level (0.8meq/liter). Since the start of treatment with lithium, the episodes of weakness have not recurred, and the patient showed significant response over 3 weeks. At 4-month follow-up, there was no recurrence of episodes of weakness, and significant improvement in mood symptoms was noted.