Paraneoplastic Limbic Encephalitis in a Human Epidermal Growth Factor Receptor-2-positive Gastric Cancer Patient Treated with Trastuzumab-combined Chemotherapy: A Case Report and Literature Review

Gastric cancer complicated by paraneoplastic neurological syndrome which presented with extremity numbness: a case report

Background

Paraneoplastic neurological syndromes refer to a group of neurological disorders, which occur as distant effects of malignant tumors and are not caused by metastasis, nutritional disorders, or side effects of antitumor drugs.

Case presentation

A 70-year-old woman complained of a 1-month history of extremity numbness. Upon presentation to our hospital, she had worsening numbness, and experienced staggering and falling. Physical examination revealed diminished tendon reflexes in both lower limbs, stocking and glove-type abnormal sensation, and left-sided dominant high-steppage gait due to weakness of the bilateral tibialis anterior muscles. Blood tests indicated anemia, and upper gastrointestinal endoscopy revealed gastric cancer, leading to laparoscopic distal gastrectomy. A nerve conduction velocity test showed demyelinating peripheral neuropathy. Further blood tests and imaging studies ruled out nutritional disorders, such as vitamin deficiency, diabetes-related diseases, connective tissue diseases, and central nervous system metastasis, leading to the suspicion of paraneoplastic neurological syndrome. After laparoscopic distal gastrectomy, the progression of symptoms stopped, and with intravenous high-dose immunoglobulin and steroid therapy, the symptoms improved to only minor numbness in the peripheral limbs as of the 18-month follow-up. As of the 2-year follow-up, there has been no cancer recurrence or metastasis.

Conclusions

When paraneoplastic neurological syndrome is suspected, early diagnosis and a multidisciplinary approach, including surgical treatment, are important before irreversible neurological damage occurs.

Clinical Characterization of Definite Autoimmune Limbic Encephalitis: A 30-case Series

Objective Limbic encephalitis (LE) is an inflammatory condition of the limbic system that has an acute or subacute onset. Several types of antibodies are related to the onset of LE, including anti-N-methyl D-aspartate receptor (NMDAR) antibodies and voltage-gated potassium channel (VGKC)-complex antibodies. However, the characteristics and prevalence of LE remain unclear, especially in Asian cohorts, due to the rarity. We aimed to survey their characteristics. Materials and Methods Data of 30 cases clinically defined as "definite autoimmune LE" (based on the standard criteria) were retrospectively collected. These patients were categorized into four subtypes: NMDAR (+) (n=8), VGKC (+) (n=2), antibodies related to paraneoplastic syndrome (n=2), and an antibody-negative group (uncategorized) (n=18). Results LE is rare in Japan, and affected only 30 of 16,759 hospital patients (0.2%) over a ten-year period. The NMDAR (+) group showed distinctive symptoms, while the other three groups had similar indications. Brain MRI indicated significant medial temporal lobe atrophy at one year follow up after discharge. The prevalence of cognitive dysfunction as a complication was 64% (9/14). First-line immunotherapy resulted in a good outcome. A drastic improvement was seen from 4.0±1.1 to 1.1+ on the modified Rankin Scale. A good treatment outcome was observed in all groups (NMDAR, VGKC, and uncategorized), suggesting the importance of an early clinical diagnosis and the early initiation of treatment. Furthermore, we reviewed 26 cases that were clinically diagnosed as definitive autoimmune LE in previous case reports. Conclusion Our findings show that the establishment of a clinical diagnosis based on the clinical criteria of definitive autoimmune LE is important for the initiation of immunotherapy.

Anti-GABAB receptor encephalitis in a patient with gastric adenocarcinoma

Anti-γ-aminobutyric acid-B (GABA_B) receptor encephalitis is an autoimmune encephalitis associated with antibodies against neuronal cell surface antigens, which are primarily observed with small-cell lung cancer, melanoma, and thymoma. Here, we first report a case on the association between a relatively frequent cancer, gastric adenocarcinoma (GAC), and a rare GABA_B receptor antibody limbic encephalitis. The patient was treated with immunotherapy and combined-drug chemotherapy, which were partially effective in terms of stabilizing the tumor and relieving neurological symptoms. This report indicates that, when patients present with GABA_B receptor antibody limbic encephalitis, regular and broad screening for tumors including gastric adenocarcinoma should also be considered.

Lower motor neuron syndrome in a patient with HER2-positive metastatic breast cancer: A case report and review of the literature

Paraneoplastic neurological syndromes are very rare and often associated to breast, ovarian and small cells lung cancers. Paraneoplastic motor neuron diseases (MNDs) are even rarer, and frequently described in patients with breast cancer. We presented the first case of patient affected by HER2-positive breast tumor and possible paraneoplastic lower motor neuron disease. In literature, few cases are reported but no one highlights the tumor receptors' profile. Instead, HER2-positive breast cancers are prone to be related to anti-Yo-associated paraneoplastic cerebellar disorders. Anti-onconeural antibodies positivity can be rarely found, confirming that paraneoplastic MND have no specific biomarkers. The presence of CSF oligoclonal bands (OBs) suggests the presence of immune-mediated mechanism, in absence of other possible OBs causes.