The 45-year-old male patient had a history of heavy smoking and drinking: approximately 20 years of drinking, an average of 1 bottle of white wine per day; approximately 20 years of smoking, an average of 1 packet per day. In March 2021, he developed an irritating dry cough, and chest CT revealed a localised area on the right lung hilum, which was suspicious of a malignant tumor; the patient then intermittently presented with a loss of consciousness, epileptic seizures, psychiatric behavioral abnormalities, and cognitive impairment. The laboratory test results were as follows: Na + 116.4 mmol/L (normal value 137.0-147.0 mmol/L); inflammatory indicators: C-reactive protein: CRP 31.6 mg/L (normal value < 10.0 mg/L); calcitoninogen: PCT > 10 ng/ml (normal value < 0.5 ng/ml); and sputum culture indicating Streptococcus pyogenes infection. After anti-infection treatment, tracheotomy and ventilator-assisted ventilation were performed. On 7 April 2021, chest CT (Fig. 2A and B) revealed right central lung cancer and metastasis to large lymph nodes in the mediastinum and bilateral hilar lymph nodes.
After 2 weeks of hospitalisation, the results of perfect lumbar puncture revealed a cerebrospinal fluid pressure of 210 mmH20 (1 mmH20 = 0.0098 kPa); cerebrospinal fluid cytology revealed 750/mm3 erythrocytes, 12/mm3 leukocytes, 77% lymphocytes, 22% monocytes, and 1% neutrophils; Penn's test was negative; cerebrospinal fluid biochemistry revealed 0.55 g/ L TP-CSF (normal value 0.12–0.60 g/L), 3.2 mmol/L GLU (normal value 2.20–3.90 mmol/L), 117 mmol/L Cl (normal value 120–132 mmol/L). Twenty-four hour dynamic EEG suggested moderately abnormal dynamic EEG monitoring, with bilateral frontal zone spike and spike slow wave issuance in the sleep period. Cranial magnetic resonance enhancement suggested deep patchy high signal foci in the left temporal lobe on T1-weighted images (Fig. 1A); T1-weighted-FLAIR images (Fig. 1B); T2-weighted images (Fig. 1C); Ddiffusion-weighted images( Fig. 1D). Lung puncture biopsy in May 2021 revealed markedly extruded and deformed cells in fibrous tissue and inflammatory necrotic material (Fig. 4), consistent with small cell carcinoma. Immunohistochemistry revealed TTF1 (+), NapsinA (-), P40 (-), P63 (-), CD56 (+), Syn (+), CgA (+), CD117 (+), and Ki67 (approximately 80%) in cancer cells. The diagnosis of SCLC was confirmed, and the 1st cycle of chemotherapy with etoposide + carboplatin regimen was started on May 8 (specific regimen: etoposide 100 mg IV d1-3, carboplatin 300 mg IV d1, 21 days for 1 cycle).
The anti-neuronal antibodies were detected by a third-party medical diagnostic company (Goldcorp Medical). On 7 May 2021, serum and cerebrospinal fluid anti-neuronal surface or prominence protein antibodies were detected using a cell-based assay (CBA). The results of 11 paraneoplastic syndrome antibody tests (serum and cerebrospinal fluid) revealed the following: anti-GAD65 antibody was IgG positive (+); anti-SOX1 antibody was IgG positive (+); anti-Ma2 antibody was IgG positive (+); and the rest of the anti-Zic4, anti-Tr (DNER), anti-Ma1, anti-amphiphysin, anti-CV2, anti-Ri, anti-Yo, and anti-Hu antibodies were negative; autoimmune encephalitis-associated antibodies 6 items (serum and cerebrospinal fluid), anti-γ-aminobutyric acid receptor (GABABR) antibody IgG positive (+) 1:100 (Fig. 3A and B); and the rest of the anti-NMDAR, anti-AMPA1, anti-AMPA2, anti-LGI1, and anti-CASPR2 antibodies were negative. Shock therapy with immunoglobulin (IVIg 0.4 g/kg*d for 5 days) was started, and dexamethasone (10 mg QD) was given as an anti-inflammatory therapy.
On 28 May 2021, sputum culture was performed, and the results suggested Acinetobacter baumannii. The patient was given a combination of cefoperazone sodium sulbactam sodium, minocycline, and cotrimoxazole, and the infection was controlled. The patient experienced repeated episodes of hyponatremia and electrolytes on June 4, suggesting that a blood sodium concentration of 104 mmol / L, should be used for symptomatic treatment.
Throughout the course of the disease, the patient's memory impairment and mental abnormalities persisted without improvement; at the end of cycle 1 of chemotherapy, the exudative foci in the lungs were absorbed compared with the previous ones (Fig. 2C and D), and respiratory function improved compared with the previous ones before stopping the ventilator-assisted ventilation and administering methylprednisolone sodium succinate 500 mg QD high-dose shock treatment for 3 days. After the 2nd cycle of chemotherapy, the lung lesions were further controlled (Fig. 2E and F), but some exudative lesions still existed. The patient was later discharged from the hospital on 8 July 2021 for financial reasons, as his mental acuity improved, and he regained consciousness. After discharge, the patient still experienced intermittent episodes of convulsive symptoms, the patient’s hyponatraemia persisted unrelieved, his symptoms gradually worsened, he continued to be maintained on oral medication, he terminated chemotherapy for lung cancer for financial reasons, and he died within 2 months of discharge during telephone follow-up.