Normal Pressure Hydrocephalus (NPH) is a neurological condition characterized by an abnormal accumulation of cerebrospinal fluid (CSF) within the brain’s ventricles. This buildup occurs despite CSF pressure often remaining within the normal range. The condition typically manifests as a specific triad of symptoms, which can significantly impact an individual’s daily life. This article explores the nature of NPH, its manifestations, and specifically addresses the question of whether it is inherited.
Understanding Normal Pressure Hydrocephalus
Normal Pressure Hydrocephalus involves a slow accumulation of cerebrospinal fluid, leading to enlarged ventricles that press on brain tissue. Unlike other forms of hydrocephalus, the pressure of the CSF often remains within the normal limits when measured, hence the name. This increased fluid volume can disrupt brain function, affecting several abilities.
The condition commonly presents with a classic triad of symptoms: gait disturbance, urinary incontinence, and cognitive impairment. Gait disturbance often appears as difficulty walking, poor balance, or a shuffling walk where the feet seem stuck to the ground. Urinary incontinence can involve urgency or loss of bladder control. Cognitive difficulties may include problems with thinking, memory, and concentration. These symptoms can sometimes be mistaken for other age-related conditions, such as Alzheimer’s or Parkinson’s disease, making accurate diagnosis important.
Is NPH Inherited?
Normal Pressure Hydrocephalus is a sporadic condition, meaning it arises without a clear pattern of inheritance within families. The majority of NPH cases are classified as “idiopathic,” indicating that their exact cause remains unknown. For the general population, the risk of inheriting NPH is currently considered very low.
Despite NPH being largely sporadic, research indicates a complex interplay between genetic and environmental factors. While a clear Mendelian, or single-gene, inheritance pattern has not been established for most NPH cases, a small number of familial cases have been reported, with some studies indicating NPH can run in families. For example, a recent systematic review identified over 30 familial cases, with two cohorts showing that 10%–16% of NPH patients had relatives with NPH symptoms.
Ongoing genomic studies have begun to identify specific genetic variants that may increase the risk of NPH or contribute to its development. These variants are often associated with functions such as blood-brain and blood-cerebrospinal fluid barriers, cilia, and ependymal cells, which are involved in CSF movement and absorption. This suggests a genetic predisposition may exist in rare instances, but it is not a direct, simple inheritance. The influence of genetics in NPH is viewed as multifactorial, meaning multiple genes, along with other factors, likely contribute to the condition.
Other Factors Contributing to NPH
Beyond the rare familial instances, NPH most commonly arises without a known cause, termed idiopathic NPH, or it can develop due to specific preceding events. Idiopathic NPH is prevalent among individuals over 60 years old. This form accounts for approximately half of all NPH cases, where medical evaluations do not identify a clear reason for the impaired circulation and absorption of CSF.
NPH can also be “secondary,” resulting from a known event that disrupts the normal flow or absorption of cerebrospinal fluid. Common preceding events include head trauma and brain hemorrhage, particularly subarachnoid hemorrhage. Infections of the brain, like meningitis, are another recognized cause. Complications from brain surgery can also lead to NPH by interfering with CSF pathways.
Identifying and Treating NPH
Diagnosing Normal Pressure Hydrocephalus involves a comprehensive evaluation due to its symptoms overlapping with other conditions. The diagnostic process includes a physical and neurological examination, a detailed review of medical history and symptoms, and brain imaging. Magnetic Resonance Imaging (MRI) scans are important for visualizing enlarged ventricles and assessing brain structures.
A lumbar puncture, also known as a spinal tap, is performed where a small amount of CSF is removed to see if symptoms temporarily improve. This “tap test” helps predict if a patient will respond to shunt surgery. NPH is one of the few causes of dementia-like symptoms that is potentially reversible with treatment.
The primary treatment for NPH is the surgical placement of a shunt. A shunt is a thin tube inserted into the brain’s ventricles to drain excess CSF to another part of the body, usually the abdomen, where it can be absorbed. This procedure helps relieve pressure on the brain, leading to improvement in symptoms. Early diagnosis and treatment are important for achieving the best possible outcomes.