Paraneoplastic limbic encephalitis, an uncommon presentation of a common cancer: Case report and discussion

Abstract

Patient: Female, 59 FINAL DIAGNOSIS: Paraneoplastic limbic encephalitis Symptoms: Seizure • memory changes • decreased concentration

Medication: Chemotherapy Clinical Procedure: Cerebral images Specialty: Hematology • Oncology.

Objective: Challenging differential diagnosis.

Background: Paraneoplastic neurological disorders (PND) are defined as remote effects on the nervous system that are not caused directly by the tumor, its metastases, or metabolic disruptions. This syndrome occurs in less than 1 per 10,000 patients diagnosed with a malignancy. Many antibodies are found in the central nervous system in PND, the most well known are Anti-Hu, Tr, CV2 Ta, Yo, Ri and amphiphysin. Paraneoplastic limbic encephalitis occurs due to involvement of the limbic system secondary to an autoimmune response to neurons of the brain provoked by the antibodies. PATIENTs, thus, present with seizures, changes in mood, memory, and personality.

Case report: Fifty-nine years-old female patient presented with seizures, decreased concentration and memory changes. Laboratory workup was remarkable for hyponatremia. Further workup included brain computerized tomography (CT) and magnetic resonance imaging (MRI), which suggested a diagnosis of encephalitis for limbic encephalitis. Anti-Hu, anti-Ma and NMDA-receptor antibodies were requested of which Anti Hu antibodies were positive. Transbronchial biopsy was obtained which confirmed the diagnosis of small cell lung cancer.

Conclusions: A very high index of suspicion should thus be present when patients present with paraneoplastic abnormalities. It must be emphasized that limbic encephalitis (LE) occurs at an early stage of the disease development and therefore the detection of paraneoplastic LE can lead to a quicker identification of the underlying malignancy and a better outcome.

Keywords: limbic system; paraneoplastic disorder; seizures and memory changes; small cell lung cancer.

Figure 1

(A, B) Axial Inversion Recovery MR images (TR/TE/TI=9000 ms/81 ms/2500 ms) demonstrate cortical hyperintensity of the limbic system involving the mesial temporal lobes, hippocampi, amygdalae, left cingulate and orbitofrontal gyri and left insular cortex (arrows), note the minimal white matter involvement disproportional to cortical involvement with loss of gray-white matter interfaces. (C, D) Axial Apparent Diffusion Coefficient maps (TR/TE=7200 ms/104 ms) show hyperintense signal indicating facilitated diffusion on corresponding inversion recovery cortical hyperintensity from T2 shine-through effect involving the limbic system (arrows) without diffusion restriction indicating absence of acute infarction, acute hyponatremic encephalopathy or pyogenic encephalitis. (E, F) Axial susceptibility-weighted MR images (TR/TE=27 ms/20 ms) demonstrate no evidence for hemorrhage, excluding hemorrhagic encephalitides. (G, H) Axial contrast-enhanced T1-weighted MR images (TR/TE=650 ms/8.4 ms) show no abnormal enhancement of the limbic structures.