Paraneoplastic Encephalopathy in a Patient With Metastatic Lung Cancer: A Case Study

CASE STUDY RS, a 36-year-old female, presented to the emergency department (ED) of a large academic medical center upon the advice of her primary care provider because of 3 weeks of progressive mental status changes, weakness, and decreased oral intake. According to her husband, RS was diagnosed with stage IIIA large cell lung cancer 8 months earlier and was treated with concurrent chemotherapy (carboplatin, pemetrexed, and bevacizumab) and radiation therapy that was completed 4 months prior to admission. No other specific information about her treatment or outside health records was available. According to her husband, RS had been in her usual state of health until approximately 3 weeks prior, when she began having significant mental status changes. She first exhibited some difficulty finding words and later was noted to be putting food in a coffee maker. This spontaneously resolved after approximately 1 week; however, she rapidly developed slurred speech and began to make nonsensical statements. These manifestations also slowly improved but were followed by worsening speech deficit, difficulty walking, and impaired balance. During one of these episodes, she had an occurrence of incontinence. Her husband also noted an incident where her "eyes were beating back and forth and the left side of her face was twitching." RS also had periods (according to her husband) where she "did not seem to be interacting with her environment." These progressively worsened during the last week, and she completely stopped walking and talking 2 days prior to coming to the ED. According to her husband, RS had rheumatoid arthritis and no surgical history. Her family history was unknown except that RS's mother had "seizures." RS had reportedly not used tobacco, alcohol, or drugs, and she was sexually active with her husband. Home medications included transdermal fentanyl 12 μg/hr patch changed every 72 hours; oxycodone-acetaminophen tablets 5-325 mg, two every 4 hours as needed for pain; prednisone 10 mg, one tablet daily; and megestrol 40 mg/mL suspension, 20 mL once daily for appetite stimulation. RS was admitted to an inpatient medical oncology service and evaluated by the oncology advanced practitioner (AP) on her second inpatient day. Upon exam, RS was nonverbal except for moaning in response to painful stimuli and to her sister's voice. Her vital signs were normal. She appeared ill but well-nourished, and she was mildly diaphoretic. Neurologic examination revealed that her pupils were slightly sluggish but equal, round, and reactive to light. Extraocular muscle movements were intact, but she did not move her eyes in response to commands. She tracked the AP and family members around the room with her eyes. Cranial nerve examination was intact with the exception of cranial nerves IX, X, and XI, which were difficult to examine given her inability to cooperate and open her mouth. Motor examination revealed increased tone throughout and intermittent, inconsistent resistance to passive movement. She was seen to move all four extremities spontaneously although not in response to commands. Deep tendon reflexes were intact and equal in all extremities. Examination of other body systems was as follows: there was dry, peeling skin on her lips, but her mucous membranes were moist and free of erythema or lesions. Her lungs were clear to auscultation bilaterally. Her heart rate and rhythm were regular, there were no murmurs, rubs, or gallops, and distal pulses were intact. Her abdomen was nondistended with normally active bowel sounds in all four quadrants. Her abdomen was soft, nontender to palpation, and without palpable masses. There was no peripheral discoloration, temperature changes, or edema, and examination of her skin was benign. Workup On admission to the emergency department, serum laboratory studies were unrevealing for any potential causes of encephalopathy. Kidney and liver function were normal, making diagnoses of uremic and hepatic encephalopathies less likely. Cultures of the urine and blood were negative. Samples of cerebrospinal fluid (CSF) were obtained via lumbar puncture and were unrevealing for any abnormalities. Computed tomography (CT) of the head without contrast was negative for any acute intracranial process. Ultrasound of the right upper quadrant revealed a single, nonspecific, hypoechoic hepatic lesion. Computed tomography scans of the chest, abdomen, and pelvis demonstrated the primary malignancy in the upper lobe of the left lung, as well as possible metastatic disease within the left lung, right lung, and liver, and widespread osseous metastatic disease. Magnetic resonance imaging (MRI) of the brain performed 1 day after admission demonstrated numerous scattered punctate foci of enhancement throughout the supratentorial and infratentorial brain parenchyma, measuring at most 3 to 4 millimeters in diameter. There was no significant mass effect or midline shift. A paraneoplastic panel was sent to an outside laboratory and returned positive for antivoltage-gated potassium channel (VGKC) autoantibodies. Differential Diagnosis Clinically, RS was exhibiting signs of encephalopathy, a broad term that indicates general brain dysfunction, the hallmark of which is altered mental status. Diagnosing encephalopathy is challenging, as many differential diagnoses must be considered. The clinician must consider metabolic derangements, toxic and infectious etiologies, psychiatric disorders, and less commonly, prion disorders and progressive dementia. Cultures of RS's blood and urine as well as other specialized endocrine tests were negative, decreasing the likelihood of a metabolic or infectious cause for her presentation. The abnormalities on her brain MRI were reviewed by a neuro-oncology team, who felt that the faint, nondescript nature of the visualized lesions was not suspicious for metastatic disease. Sequelae of seizures was also considered by neuro-oncology but dismissed given a grossly normal prolonged electroencephalogram. Some encephalopathies are caused by autoimmune or inflammatory mechanisms, which are confirmed by the presence of autoantibody markers and/or clear response to immunomodulatory treatment (Vernino, Geschwind, & Boeve, 2007). These types of encephalopathies have been seen in patients with cancer and have thus been termed paraneoplastic. The presence of anti-VGKC antibodies on RS's paraneoplastic panel directed the inpatient medical oncology team toward a paraneoplastic neurologic disorder (PND) as the most likely diagnosis.