Hydrocephalus mimicking a reversible frontal behavioral syndrome without neurodegenerative pattern

Background

Idiopathic normal pressure hydrocephalus (iNPH) is a potentially reversible neurological disorder characterized by gait disturbance, cognitive impairment, and urinary incontinence, and defined radiologically by ventriculomegaly. Symptoms often improve after cerebrospinal fluid (CSF) diversion, making iNPH a key treatable cause of reversible dementia [1].Despite this classic triad, iNPH may mimic neurodegenerative disorders such as frontotemporal dementia (FTD). Ventricular enlargement can disrupt frontal–subcortical circuits, leading to behavioral and executive dysfunction, with considerable clinical and imaging overlap between iNPH and FTD [2][3].However, the absence of a dementia-specific hypometabolic pattern on PET imaging may favor frontal–subcortical network dysfunction over primary neurodegeneration [4].We present a case of frontal behavioral symptoms after a seizure-like onset, later diagnosed as tumor-related hydrocephalus, emphasizing the importance of careful differential diagnosis.

Case Description:A 59-year-old married, retired male presented with a fluctuating neuropsychiatric syndrome following a seizure-like episode. Initial evaluation revealed hydrocephalus secondary to a mass compressing the third ventricle, and a ventriculoperitoneal shunt was placed after partial tumor resection. Following surgery, the patient initially stabilized; however, within months, he developed progressive behavioral changes, including disinhibition, socially inappropriate behavior, hyperphagia, stereotypies, and executive dysfunction, evolving into a clinical picture resembling behavioral variant frontotemporal dementia. The course was marked by significant fluctuations. Periods of deterioration, including delirium and worsening cognition, were temporally associated with shunt-related complications and ventricular changes, while neurosurgical interventions and shunt adjustments led to clinical improvement. Neuropsychological assessment revealed executive dysfunction and memory impairment with relatively preserved language function (MoCA: 15, FAB: 11). FDG-PET showed no dementia-specific regional hypometabolic pattern. In the later course, behavioral symptoms improved with optimization of shunt function and brexpiprazole treatment, with only mild residual memory deficits at follow-up.

Methods

A comprehensive diagnostic approach was employed, including longitudinal clinical observation, structural neuroimaging (computed tomography and magnetic resonance imaging), functional imaging with fluorodeoxyglucose positron emission tomography, and neuropsychological assessment using standardized tools.

Results

The clinical course showed a progressive yet fluctuating pattern of behavioral and cognitive impairment, including disinhibition, socially inappropriate behavior, stereotypies, and executive dysfunction, consistent with a frontal behavioral syndrome. Neuropsychological assessment revealed deficits in executive functions, inhibitory control, and memory, with relatively preserved language and naming, suggesting selective frontal network involvement.Symptom severity varied in parallel with ventricular dynamics and shunt function; periods of deterioration, including delirium and behavioral worsening, were associated with hydrocephalus-related changes, while neurosurgical interventions led to clinical improvement, supporting a reversible process.Neuroimaging demonstrated ventricular enlargement without significant cortical atrophy, and FDG-PET showed no dementia-specific hypometabolic pattern. Overall, findings supported frontal–subcortical network dysfunction rather than primary neurodegeneration.

Conclusions

This case highlights that hydrocephalus may present as a reversible frontal behavioral syndrome mimicking frontotemporal dementia. The absence of a dementia-specific hypometabolic pattern and symptom fluctuation in parallel with ventricular changes support a non-degenerative etiology. These findings emphasize the importance of integrating clinical course and multimodal assessment to avoid misdiagnosis and ensure appropriate treatment.

References

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