Case Presentation: A 77 year-old female without significant history presented with six months of urinary incontinence, six weeks of progressive confusion and falls, and one day of decreased speech and poor appetite. During two recent hospitalizations for acute encephalopathy, imaging revealed a frontal lobe meningioma, acoustic neuroma, and diffuse ventricular enlargement.On admission, the patient was drowsy, disoriented, and unable to maintain posture. Neurological examination revealed no slurred speech, focal weakness, cranial nerve deficits, or meningismus. Repeat brain imaging was unchanged. A large-volume lumbar puncture (LVLP) yielded no clinical improvement. Cerebrospinal fluid (CSF) analysis was notable for elevated protein levels (182 mg/dL [15–45]) but was otherwise negative for infectious, autoimmune, or paraneoplastic etiologies. Serum studies were significant for GABAB-R antibody positivity. Chest CT and PET identified a hypermetabolic lesion in the right lower lung lobe. Bronchoscopy with biopsy confirmed a typical carcinoid tumor. The patient received IV methylprednisolone and therapeutic plasma exchange followed by rituximab for suspected paraneoplastic encephalitis, which resulted in minimal cognitive improvement. Neurosurgery then placed a ventriculoperitoneal (VP) shunt for suspected normal pressure hydrocephalus (NPH), resulting in significant improvement in cognition, gait, and responsiveness.
Discussion: This case highlights the diagnostic complexity of overlapping neurological syndromes. The patient exhibited the classic triad of NPH (urinary incontinence, dementia, and gait dysfunction), but rapid symptom progression and lack of response to LVLP raised concerns for an alternate diagnosis. Serum GABAB-R antibody positivity suggested paraneoplastic limbic encephalitis, typically linked to small cell lung carcinoma or atypical carcinoid tumors. However, no prior cases have associated GABAB-R antibodies with typical carcinoid tumors or shown serum antibody positivity without CSF positivity. The patient’s coexisting brain tumors may have contributed to the lack of response to LVLP due to mass effect altering CSF dynamics. Ultimately, neurosurgical evaluation and VP shunting confirmed and treated NPH with symptom resolution. This underscores the need for a high index of suspicion for NPH, even when initial diagnostic steps, such as LVLP, are inconclusive.The limited response to treatment for GABAB-R antibody-mediated encephalitis complicated the clinical picture. While corticosteroids, plasma exchange, and rituximab are standard therapies, the concurrent brain masses and NPH may have obscured immune therapy benefits. The significance of isolated serum GABAB-R antibodies remains unclear, warranting further study.
Conclusions: This case highlights the intricate diagnostic and therapeutic challenges posed by complex neurological presentations in hospital medicine. It demonstrates that the diagnosis of NPH cannot always rely on response to LVLP, particularly in the presence of coexisting conditions that may obscure clinical clarity. The case underscores the critical role of vigilance, adaptability, and multidisciplinary collaboration in addressing overlapping neurological, autoimmune, and oncologic conditions, enabling hospitalists to navigate diagnostic uncertainty and achieve favorable outcomes.