Hyponatremia and extrapontine myelinolysis in a patient with
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A 43-year-old man with a known history of type 2 diabetes and essential hypertension, controlled with oral hypoglycemics and combined antihypertensive drugs, respectively, presented with complaints of fever and cough for two days. Initial investigations revealed that he had mildly symptomatic COVID-19 pneumonia diagnosed by testing a nasopharyngeal swab sample using polymerase chain reaction (PCR) and chest X-ray. So, he was admitted for treatment and isolation.

In his initial investigations, he had significant hyponatremia (123 mmol/L) with raised serum creatinine (143 µmol/L) level while urea, potassium, and liver function tests (LFT) were within normal limits. Management was initiated with a standard COVID-19 treatment regimen including azithromycin, amoxicillin/clavulanate, hydroxychloroquine (HCQ), and lopinavir/ritonavir in appropriate doses.

He remained asymptomatic for more than a week and serum electrolytes were never repeated till the ninth day of admission when he became disoriented and started having incomprehensible speech and an unsteady gait. At this point, a computed tomography (CT) scan of the head along with blood investigations, including serum electrolytes, was urgently obtained. The CT scan was reported as normal, but the patient's serum sodium level was critically low (93 mmol/L) which fell to an extremely low value of 88 mmol/L in the next four hours. Serum potassium and renal function tests (RFT) were within normal limits with deranged LFTs, most likely related to medications.

The patient was shifted to the intensive care unit (ICU) for correction of hyponatremia and neurologic observation. His initial Glasgow Coma Scale (GCS) score was 14/15, with some disorganized speech and an unsteady gate. Power, reflexes, and muscle tone were within normal limits. He received hypertonic saline (3% normal saline) for the next two days, resulting in a sodium level of 126 mmol/L (on the third day) which subsequently improved his condition clinically by day four. He was fully oriented to time, place, and person with explicit language. His GCS dropped to 10/15 on the fifth day, and he became less responsive with disorientation to time. On examination, he was moving all four limbs with osteotendinous reflexes of 3/4 in all the extremities. A repeat CT head scan revealed no ischemic changes. This was followed by a magnetic resonance imaging (MRI) of the brain which was also reported as unremarkable.

On day seven, his GCS further declined to 8/15 and he was intubated and transferred to a tertiary care facility for further management. The MRI was repeated after almost two weeks from the start of the symptoms. T1-weighted images (T1WI) revealed hypointense signals this time, whereas T2-weighted images (T2WI), T2-weighted fluid-attenuated inversion recovery (T2 FLAIR), and diffusion-weighted images (DWI) revealed high signal intensity in the caudate nuclei, putamen, and external capsule bilaterally, with a corresponding low signal on the apparent diffusion coefficient (ADC) map, indicating edema and restricted diffusion due to osmotic demyelination.

Of particular note in this MRI study were the findings of bilateral amygdala hyperintensity on T2WI and FLAIR sequence. This, with bilateral cortical gray matter swelling, goes with COVID-19-related encephalopathic changes. Over the next two days, the patient developed an increase in muscle tone, especially in the upper limbs. A low dose of carbidopa/levodopa (12.5/50 mg thrice daily) was started to ameliorate muscle rigidity. Five days later, he was successfully extubated and shifted to the medical floor.

A follow-up MRI performed nearly two months after the onset of symptoms revealed a significant interval decrease in the previously described symmetrical swelling and abnormal signal intensity in the bilateral caudate nuclei, putamen, external capsule, and cortical gray matter. There was a signifying improvement in edema of osmotic demyelination. The susceptibility-weighted imaging (SWI) sequence, which was unremarkable in previous Imaging, displayed susceptibility changes in the parietal, subcortical, putamen, and caudate regions in this MRI, suggestive of microhemorrhages due to COVID-19-related encephalopathy.

After four months of follow-up, the patient showed considerable improvement in his cognitive and functional status. At the time of reporting this case, he was alert and oriented, but still needed assistance for physical activity.

Source: https://onlinelibrary.wiley.com/doi/10.1002/ccr3.4463?af=R
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