Definition and Overview
Normal pressure hydrocephalus is a condition in which the ventricle expands due to a cerebrospinal fluid circulation disorder, but the measured intracranial pressure remains within the normal range. It is characterized by the three signs of gait disturbance, cognitive decline, and urinary incontinence, and symptoms can improve if the cause is corrected, so it is considered a representative cause of dementia that can be corrected.
Idiopathic normal pressure hydrocephalus (idiopathic NPH, iNPH), which occurs without a clear preceding cause, accounts for the majority and occurs mainly in elderly people. It can also be secondary, occurring after trauma, hemorrhage, or meningitis. In ICD-10, it is classified as G91.2.
3 major symptoms
Normal pressure hydrocephalus is characterized by the three symptoms of gait disturbance, cognitive decline, and urinary incontinence.
- Gait disturbance: Usually appears first and most noticeably. They have trouble taking their feet off the floor, their strides become narrow, and they have difficulty changing direction and maintaining balance.
- Cognitive decline: Mainly a decline in attention, processing speed, and executive function, accompanied by apathy and slowed reactions.
- Urinary incontinence: It begins with urinary urgency that makes it difficult to hold in urination, and gradually progresses to urinary incontinence.
All three symptoms may not appear at the same time, and gait disturbance often precedes it.
Causes and Pathophysiology
The core mechanism of normal pressure hydrocephalus is the loss of balance between the production and absorption of cerebrospinal fluid, resulting in excessive accumulation of cerebrospinal fluid in the ventricles. As the ventricle gradually expands due to impaired circulation and absorption of cerebrospinal fluid, the surrounding white matter and nerve pathways receive pressure and traction, causing symptoms.
When measuring intracranial pressure, it is within the normal range, giving it the name normal pressure, but in reality, intermittent pressure fluctuations and circulatory disorders are involved. It is explained that ventricular enlargement affects the neural pathways that control gait, causing gait disturbances to become noticeable first.
diagnosis
Diagnosis is made based on the clinical triad, imaging findings, and cerebrospinal fluid drainage response.
- Brain MRI: Confirms findings that the ventricles are disproportionately enlarged compared to other atrophies, and evaluates the degree of ventricular enlargement.
- Cerebrospinal fluid drainage test (tap test): After draining a certain amount of cerebrospinal fluid through lumbar puncture, changes in gait and cognitive function are evaluated. If improvement is confirmed after drainage, there is a high possibility that the patient will respond to shunt surgery.
- Differential diagnosis: Distinguish from other diseases that cause gait disorders and cognitive decline, such as Alzheimer's disease, vascular dementia, and Parkinson's disease.
Even if ventricular enlargement is visible on imaging, symptoms and drainage response must be checked together, so a judgment that integrates clinical evaluation and examination is necessary.
treatment
The standard treatment is ventriculoperitoneal shunt surgery. Excess cerebrospinal fluid is drained into the abdominal cavity through a tube inserted into the ventricle, and the amount of drainage is controlled with a pressure control valve.
Improvement in gait after shunt surgery is reported in approximately 60-80% of cases, and gait disorders tend to improve first and most clearly. Cognitive decline and urinary incontinence may also improve, but the degree of response varies depending on the patient. There is a possibility of complications such as infection, bleeding, and excessive drainage during surgery, so indications must be carefully evaluated.
The prognosis is better if diagnosed early and treated at an appropriate time, so it is important to recognize the three signs and lead to an early diagnosis without mistaking it for aging or other dementia.