Rare paraneoplastic syndrome of prostatic cancer: limbic encephalitis: a case report

Abstract

Introduction: Limbic encephalitis is an autoimmune neurologic disorder, often of paraneoplastic origin, that seldom complicates prostatic tumors. The nonspecificity of symptoms makes the diagnosis sometimes difficult to establish. Prognosis is essentially determined by comorbidities and sensorineural and cognitive sequelae.

Clinical case: A 66-year-old Caucasian patient known to have prostatic small-cell neuroendocrine adenocarcinoma under hormonal therapy developed complex partial epileptic seizures associated with rapidly aggravating severe memory impairment. The tripod of autoimmune limbic encephalitis diagnosis was based on the clinical aspect of brain's functional deterioration, electroencephalography aspect, and γ-aminobutyric acid type B anti-receptor antibody positivity. Clinical, diagnostic, and therapeutic management as well as evolutionary risks were further analyzed.

Conclusion: Limbic encephalitis is an extremely rare presentation of neurologic paraneoplastic syndromes. A better knowledge of this entity would help better manage diagnostic and therapeutic difficulties and reduce the risk of possible sequelae.

Keywords: GABA receptors; Limbic encephalitis; Prostatic neoplasms; Seizures.

Fig. 1

Example of left temporal seizure with rhythmic discharges of left temporal slow waves and slow spikes

Fig. 2

MRI: left hippocampal and parahippocampal hypersignal, without contrast enhancement

Fig. 3

Microscopic histological examination; hematoxylin–eosin coloration: poorly differentiated carcinomatous proliferation, with significant necrotic eosinophilic change

Fig. 4

Immunohistochemical findings: positivity for neuroendocrine markers (chromogranin A)

Fig. 5

Immunohistochemical findings: High Ki67 proliferation index, marking 100% of tumor cells