Voltage-gated potassium channel autoimmunity and indolent cognitive impairment: a consecutive case series from the University Hospitals Leuven memory clinic
Introduction
VGKC-Ab (voltage-gated potassium channel antibodies) are an emerging topic in current neurology. They are typically associated with limbic encephalitis, peripheral nerve hyperexcitability and Morvan syndrome. Recent publications however point to a broader clinical spectrum, e.g. psychosis, epileptic syndromes and many others. Here we explore the potential of VGKC-Ab to induce chronic cognitive impairment characterized by episodic memory loss and a more indolent course.
Patients and Methods
We retrospectively evaluated a series of 70 cases (mean age 60 years, range 42-83) presented at the University Hospitals Leuven memory clinic in whom anti-VGKC antibodies had been tested (October 2009 till February 2012). The indication for the test was the presence of an objective episodic memory deficit in the absence of any other causal explanation. VGKC-Ab titers were assessed by a radioimmunassay performed by the University of Oxford Churchill Hospital.
Results
Eight patients (6 males, 2 females; age range 45-77 years) tested positive. They had a history of cognitive complaints of 6 months till 6 years. A formal neuropsychological investigation performed in 7 patients could demonstrate a cognitive deficit in all but one. One case showed a classical course starting with an amnestic syndrome followed within three months by epileptic seizures and fluctuating alertness but in the remaining cases the deficit was relatively stable.
Titers ranged from 143pM till 5377pM (normal: 0-100pM). In 3 patients titers were beneath 400pM, 4 patients had a titer of more than 400pM. In one the titer was not known. Liquor investigation was normal in one and showed an isolated protein elevation in 4. In 3 cases there were additional abnormalities in cell count (5,6 - 7,2/µl; n = 2), glucose (n=2), IgG-index (n=1) or oligoclonal bands (n=2). VGKC-Ab in CSF were tested in two cases and negative. All patients underwent a brain MRI, which revealed hippocampal atrophy in 1 patient en more widespread volume loss in 2 patients. Onco-PET was performed in all patients, in one a tumor was discovered.
Conclusion
VGKC-Ab may be of clinical relevance in the diagnosis of cognitive impairment with a more indolent course than typically reported. However, because of the retrospective nature of this case series, we stress the importance of future prospective study. Given the uncertainty about the significance of titers between 100-400 pM, test reports should also include titers and not only a binary distinction between positive versus negative.
References
1. Vincent A, Buckley C, Jonathan MS, et al. Potassium channel antibody-associated encephalopathy: a potentially immunotherapy-responsive form of limbic encephalitis. Brain 2004; 127(3): 701-712.
2. Vincent A, Bien CG, Irani SR, Waters P. Autoantibodies associated with diseases of the CNS: new developments and future challenges. Lancet Neurol 2011; 10(8): 759-72.
Keywords:
VGKC-Ab,
indolent cognitive impairment,
memory clinic,
Radioimmunoassay,
neuronal autoantibodies
Conference:
Belgian Brain Council, Liège, Belgium, 27 Oct - 27 Oct, 2012.
Presentation Type:
Poster Presentation
Topic:
Other basic/clinical neurosciences topic
Citation:
Neyens
V and
Vandenberghe
R
(2012). Voltage-gated potassium channel autoimmunity and indolent cognitive impairment: a consecutive case series from the University Hospitals Leuven memory clinic.
Conference Abstract:
Belgian Brain Council.
doi: 10.3389/conf.fnhum.2012.210.00015
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Received:
10 Sep 2012;
Published Online:
12 Sep 2012.
*
Correspondence:
Miss. Veerle Neyens, KU Leuven, Leuven, Belgium, veerle.neyens@student.kuleuven.be