A referred case of 34-year-old female with history of migraine without aura who was apparently well 1 month back presented to the local hospital with the history of vomiting about 8-10 episodes per day for 10 days. Vomiting was associated with bilateral headache which was persistent, throbbing in nature and used to get relieved on oral pain medication. Patient then visited nearby hospital where her routine blood examinations revealed hyponatremia (Na+ = 108 mEq/L; reference = 135-145 mEq/L) along with borderline hypokalemia (3.4 mEq/L; reference = 3.5-5.2 mEq/L). Her blood glucose (5.5 mmol/L; reference = 3.8-7.8 mmol/L), creatinine (83 microMol/L; reference = 40-110 microMol/L) and urea (6.2 mmol/L; reference = 1.6-7 mmol/L) were within normal limits. She was admitted to intensive care unit (ICU) where she was symptomatically managed for 10 days. Hyponatremia was corrected from 108 to 132 mEq/L within 48 h of time. After 3 days, she was unable to speak and developed sustained stiff limbs. She was unresponsive to command and developed involuntary outbursts of laughter and crying. She was then treated with gradually increased dose of lorazepam, but there was no improvement.
For further neuropsychiatric evaluation, she was referred to our center. On examination in the emergency room, the patient was ill looking with tremors on both hands and legs with involuntary outbursts of laughter and crying. Her Glasgow Coma Scale (GCS) was 12/15; eye opening was 4, verbal was 3 and motor was 5.   Her pulse rate was 123/min, blood pressure was 120/90 mm Hg, and was afebrile. Other systemic examinations were within normal limits. Brain magnetic resonance imaging (MRI) scan, done on 10th day of her neuropsychiatric symptoms, showed symmetric T2/fluid-attenuated inversion recovery (FLAIR) and diffusion-weighted imaging (DWI) hyperintense signals at bilateral lentiform nucleus and head of caudate nucleus and normal signal in pons (Figure 1(a)-(c)). Apparent diffusion coefficient (ADC) scan also showed hyperintensity in bilateral lentiform and caudate nucleus (Figure 1(d)). With the clinical history of rapid correction of hyponatremia, clinical manifestations and neuroimaging findings, diagnosis of isolated EPM was made.
Patient was treated with quetiapine 75 mg/day, thiamine 400 mg/day, methylcobalamin 1500 mcg/day, trihexyphenidyl 6 mg/day, levodopa-carbidopa 250 mg/day and physiotherapy of limbs. During hospital stay, the patient's sensorium and crying episodes were gradually improved. At the time of discharge (10th day of admission), the patient had GCS of 15/15, was able to walk with support, feed by herself, tremor and rigidity were reduced. She started communicating with her family members with unresolved dysarthria. Medicines were reduced to quetiapine 25 mg/day, thiamine 100 mg/day, methylcobalamin 500 mcg/day, trihexyphenidyl 2 mg/day and static dose of levodopa-carbidopa at 250 mg/day. On follow-up after 3 months, the patient had resolution of all other symptoms except rigidity in left hand and mild dysarthria that were improving in its course. Levodopa-carbidopa was prescribed to continue at the same dose (250 mg/day), and the rest of the medications were stopped.