Subacute cognitive impairment, hyponatremia and mesial temporal lobe lesions: a typical presentation of voltage-gated potassium channel (VGKC) antibody-associated limbic encephalitis

Abstract

For many years, several reports have called attention for non-viral limbic encephalitis (LE), particularly with paraneoplastic etiology. However, an increasing number of data have demonstrated that some of those disorders are immune-mediated with antibodies to voltage-gated potassium channels (VGKC)1 . Herein, we present a case of VGKC antibody-associated LE and discuss the main phenotypic and imaging features of this unusual disease. CASEA 50-year-old man presented to our hospital with three months history of progressive personality change, sleep disturbance, memory impairment, visual hallucinations and seizures. Neurological examination showed disorientation, cognitive impairment (Mini Mental State Examination: 13) and memory dysfunction. Blood tests showed hyponatremia -130 mmol/L (135-145 mmol/L). Thyroid function, antibodies and serologic tests were normal. Cerebrospinal fluid showed high level of proteins (558 mg/dL) and mild lymphocytic pleocytosis. Brain magnetic resonance imaging (MRI) disclosed bilateral T2 and FLAIR hyperintensity of mesial temporal lobes (Figure). Cancer investigation resulted negative. VGKC serum level was higher than 650 pmol/L (normal range less than 450 pmol/L). These findings confirmed the diagnosis LE with VGKC antibodies. Methylprednisolone was started, with partial improvement. Three weeks later, immunoglobulin 0.4 g/Kg daily for five consecutive days was initiated. One week after immunoglob-

A case study of voltage-gated potassium channel antibody-related limbic encephalitis with PET/MRI findings

“…Classically, regional abnormalities in the mesial temporal lobes in VGKC-LE are not seen in other VGKC antibody-related neurological disorders, namely Morvan's or Isaac's syndromes [11] . Imaging abnormalities typical of VGKC-LE have also been reported in patients manifesting personality changes and memory deficits without evidence of seizures [12,13] . Furthermore, patients with VGKC-LE have been reported to have a normal brain MRI but bitemporal hypometabolism on brain PET [14] , similar to findings in our patient.…”

"Unusual" viral diseases after allogeneic hematopoietic stem cell transplantation: a multicenter, retrospective study

“…One possible mechanism is that the in ammation caused by HHV-6 encephalitis directly stimulates the hypothalamic-pituitary system, and another possible mechanism is that it causes dysregulation of vasopressin production by impacting limbic function. 14,15 The limbic region has the potential to inhibit the hypothalamic-pituitary system (hypothalamic nucleus) involved in the production of ADH, so HHV-6 encephalitis involving the limbic region can cause SIADH. After antiviral treatment with reduction of immunosuppressants, IVIG, ganciclovir, cidofovir, foscarnet, etc., the infection of 7 patients is all improved, the serum sodium level of 4 patients with refractory hyponatremia recovered, 6 patients survived without sequelae, and 1 patient died of recurrence of the primary disease.…”