N-type calcium channel antibody-mediated paraneoplastic limbic encephalitis: a diagnostic challenge.
BACKGROUND
The etiology of encephalitis presents a diagnostic challenge and often remains a mystery. However, current technological advances using antibodies can enable a definitive diagnosis in cases that would previously have been suspected to be idiopathic or viral encephalitis. Our objective is to show that tonsil neuroendocrine carcinoma can present initially as limbic encephalitis mediated by N-type calcium channel antibodies and to highlight the diagnostic confusion before cancer detection.


METHODS
We report a rare case of neuroendocrine cancer presenting as limbic encephalopathy, Lambert-Eaton myasthenic syndrome and neuropathy. The patient was diagnosed and treated at The University of Texas MD Anderson Cancer Center in November 2011.


RESULTS
Paraneoplastic limbic encephalitis was diagnosed based on clinical presentation of seizures, short-term memory loss, retrograde amnesia, disorientation, distractibility, and abulia; on the exclusion of brain metastases, CNS infection, stroke, metabolic or nutritional deficits, or medication-related events; and on CSF results with inflammatory findings and an abnormal electroencephalography study that showed seizure activity in the left temporal lobe. Serum paraneoplastic panel was positive for P/Q-type calcium channel antibody and N-type calcium channel antibody. Magnetic resonance imaging of brain was unremarkable.


CONCLUSIONS
This case highlights limbic encephalitis as an atypical presentation of neuroendocrine cancer. It also illustrates how treatment of the underlying cancer can reverse limbic encephalitis and Lambert-Eaton myasthenic syndrome in a neuroendocrine carcinoma patient even before the paraneoplastic panel becomes negative.
Department of Neuro-Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, United States. Electronic address: ckamiya@mdanderson.org.
Carlos
C
Kamiya-Matsuoka
Department of Neuro-Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, United States.
David
D
Blas-Boria
Department of Pathology, The University of Texas MD Anderson Cancer Center, Houston, TX, United States.
Michelle D
MD
Williams
Department of Neuro-Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, United States.
Pedro
P
Garciarena
Department of Neuro-Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, United States.
Sudhakar
S
Tummala
Department of Neuro-Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, United States.
Ivo W
IW
Tremont-Lukats
D000906:Antibodies / Q000134:cerebrospinal fluid*; D020864:Calcium Channels, N-Type / Q000276:immunology*; D006801:Humans; D020363:Limbic Encephalitis / Q000134:cerebrospinal fluid* / Q000000981:diagnostic imaging; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography
D000906:Antibodies; D020864:Calcium Channels, N-Type
Calcium channel antibodies; Lambert–Eaton myasthenic syndrome; Limbic encephalitis; Neuroendocrine cancer; Paraneoplastic syndrome; Small-cell lung cancer