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Some elderly people who exhibit symptoms such as difficulty walking, dementia, and urinary incontinence are suffering from a disease called idiopathic normal pressure hydrocephalus. Our department focuses on treating this condition because cerebrospinal fluid shunt surgery can improve symptoms, particularly walking difficulty.
1) What kind of disease is idiopathic normal pressure hydrocephalus?
Elderly people may recently experience symptoms such as difficulty walking, cognitive impairment, and urinary incontinence, even though they have no known underlying brain disease. These symptoms can be seen in Parkinson's disease, vascular dementia, or Alzheimer's disease, but a small percentage of cases are caused by a condition called idiopathic normal pressure hydrocephalus. If this disease is properly diagnosed, it is believed that symptoms can be improved with a surgery called a cerebrospinal fluid shunt.
2) What are the characteristics of the symptoms?
Typically, the three symptoms of gait disturbance, dementia, and urinary incontinence are present, but gait disturbance alone may also be present.
Gait disturbance is the most common symptom. While walking can be difficult even with joint pain or leg paralysis, gait disturbance in idiopathic normal pressure hydrocephalus is characterized by small, shuffling steps and increased unsteadiness when walking, especially when changing direction. While the gait is somewhat similar to that of Parkinson's disease, external stimuli such as hand clapping do not improve gait. Another characteristic is walking with the feet apart, which is different from the gait of Parkinson's disease.
It is not surprising that elderly people may show some symptoms of dementia, but it is believed that most of them have mild dementia such as forgetfulness and decreased attention span, rather than severe dementia such as Alzheimer's disease, which causes personality changes and confusion about people.
There are many causes of urinary incontinence, but idiopathic normal pressure hydrocephalus can also cause urinary incontinence.
3) Can a diagnosis be made using CT or MRI?
Hydrocephalus is suspected when reservoir-like areas within the brain parenchyma (called ventricles) are enlarged. Therefore, the presence of ventricular enlargement on either CT or MRI is a prerequisite for suspecting idiopathic normal pressure hydrocephalus. Traditionally, ventricular enlargement can be seen even when there is overall brain atrophy, making it difficult to distinguish between the two. Recently, it has been reported that in addition to ventricular enlargement, there is also a reduction in the cerebrospinal fluid space in the high convexity (parietal region), in contrast to which the cerebrospinal fluid space at the base of the brain is enlarged. MRI is useful for confirming this finding. If idiopathic normal pressure hydrocephalus is suspected based on symptoms and imaging findings, the following cerebrospinal fluid tap test is performed.
4) What is the cerebrospinal fluid tap test, which is useful for diagnosis?
The cerebrospinal fluid tap test involves inserting a slightly thick needle into the lower back, removing approximately 30 ml of cerebrospinal fluid, and observing any subsequent changes in symptoms, particularly gait. In idiopathic normal pressure hydrocephalus, walking improves within a few days, but the effect is temporary and the patient gradually returns to normal. If there is a clear improvement in symptoms, even if only temporarily, surgery to improve the flow of cerebrospinal fluid can be expected to improve the symptoms. Even if symptoms do not improve with this test, surgery may still be effective.
5) Are there any other good testing methods besides the cerebrospinal fluid tap test?
In addition to the CSF tap test, other useful testing methods include continuous CSF drainage, continuous CSF pressure measurement, and CSF absorption resistance measurement. Continuous CSF drainage involves inserting a silicone tube into the lower back to continuously drip CSF. 150-200ml is drained per day for several days, after which a check is made to see if symptoms have improved. Continuous CSF pressure measurement involves inserting a silicone tube into the lower back to measure CSF pressure. In our department, we use this method to administer a drug that dilates cerebral blood vessels intravenously at the end of the test, measure the degree of CSF pressure increase, and use this to assess the effectiveness of shunt surgery.
6) What treatments are available?
Currently, the only treatment is surgery. This involves a CSF shunt, which directs the CSF that has accumulated in the ventricles to another area via an artificial silicone tube, helping the CSF to be absorbed. The most common procedure is a ventriculoperitoneal shunt, which directs CSF toward the abdomen, and is one of the many procedures performed in neurosurgery. A pressure-regulating valve is installed midway through this silicone tube. Recently, these pressure-regulating valves have become capable of changing the set pressure externally (variable pressure), and the use of such variable pressure valves is considered preferable for idiopathic normal pressure hydrocephalus, which requires delicate pressure regulation. Other CSF shunt procedures include ventriculoatrial shunts and ventriculolumbar subarachnoid shunts.
7) In what cases is surgery performed?
The decision to perform surgery is made based on the patient's symptoms and test results, as well as whether general anesthesia is possible, whether the patient and their family wish for it, whether there are any serious systemic complications, and whether the nursing care environment is in place. The surgery takes about two hours. The patient will be hospitalized for about two weeks.
8) What are the therapeutic effects?
Gait disturbance is an early symptom that shows results, with an efficacy rate of over 80%. Urinary incontinence is also effective in about 50% of cases. Improvement of dementia symptoms such as forgetfulness and decreased attention span is slightly slower, with an efficacy rate of 30-50% after one year.
9) Is the surgery safe?
Cerebrospinal fluid shunt surgery is one of the most commonly performed neurosurgery procedures. It is considered a highly safe procedure, but complications do occur in a few percent of cases. Serious complications include loss of consciousness, motor paralysis, meningitis, and peritonitis. In elderly patients, pneumonia may also occur.
10) What precautions should I take after surgery?
As symptoms improve after surgery and daytime activity increases, cerebrospinal fluid flows more easily, and patients may complain of headaches when standing or walking. Gradual improvement can be seen by setting the valve pressure appropriately. Edema or hematoma may also be observed inside the head. Regular CT scans are required for several months after surgery. While this may disappear simply by changing the valve pressure setting, if symptoms such as loss of consciousness or paralysis of the limbs appear, surgery is required.
On the other hand, there are cases where symptoms do not improve even after surgery, or where symptoms temporarily improve but then return to normal. This may be due to a decrease in the flow of cerebrospinal fluid, so we check to see if the tubes are clogged. Also, since increased abdominal pressure due to obesity or constipation may be a factor, it is necessary to check the patient's weight and bowel movements as well as change the set pressure.
In addition, infections such as meningitis or peritonitis may occur, and the silicone tube may need to be removed to treat the infection.
When providing care, it is important to note that even if there is improvement in walking, instability may still remain, so care must be taken to prevent falls.
Idiopathic normal pressure hydrocephalus may be an unfamiliar name. Generally, many middle-aged and elderly people complain of symptoms such as a slower walking speed or an unsteady gait that makes them prone to falls. Some of these people have cerebrospinal fluid circulatory disorders, and their symptoms can be improved by cerebrospinal fluid shunt surgery. In cases where dementia and urinary incontinence are also present, these symptoms may also improve. Caution is required if a head CT scan or other test reveals ventricular enlargement after a fall.
Idiopathic normal pressure hydrocephalus causes gait disturbance without any apparent cause, and symptoms can be improved with cerebrospinal fluid shunt surgery, making it important in reducing the burden of caregiving in an aging society. While it is still not easy to predict which patients will benefit from cerebrospinal fluid shunt surgery before surgery among many similar cases, our neurosurgery department performs surgery on appropriate patients through auxiliary diagnoses, including imaging diagnostics and cerebrospinal fluid drainage tests, and collaboration with neurologists. Furthermore, even if similar symptoms are present, there are cases in which the condition may actually be obstructive hydrocephalus or tumor-related hydrocephalus, and we offer reliable diagnosis and appropriate treatment (neuroendoscopic surgery, etc.).
