More information on Hydrocephalus

Reference: "Hydrocephalus" by Eugenia-Daniela Hord, MD, Instructor, Departments of Anesthesia and Neurology, Massachusetts General Hospital Pain Center, Harvard Medical School

Pathophysiology

Normal CSF production is 0.20-0.35 mL/min; a majority is produced by the choroid plexus, which is located within the ventricular system, mainly the lateral and fourth ventricles. The capacity of the lateral and third ventricles in a healthy person is 20 mL. Total volume of CSF in an adult is 120 mL.

Normal route of CSF from production to clearance is the following: From the choroid plexus, the CSF flows to the lateral ventricle, then to the interventricular foramen of Monro, the third ventricle, the cerebral aqueduct of Sylvius, the fourth ventricle, the 2 lateral foramina of Luschka and 1 medial foramen of Magendie, the subarachnoid space, the arachnoid granulations, the dural sinus, and finally into the venous drainage.

ICP rises if production of CSF exceeds absorption. This occurs if CSF is overproduced, resistance to CSF flow is increased, or venous sinus pressure is increased. CSF production falls as ICP rises. Compensation may occur through transventricular absorption of CSF and also by absorption along nerve root sleeves. Temporal and frontal horns dilate first, often asymmetrically. This may result in elevation of the corpus callosum, stretching or perforation of the septum pellucidum, thinning of the cerebral mantle, or enlargement of the third ventricle downward into the pituitary fossa (which may cause pituitary dysfunction).

The mechanism of NPH has not been elucidated completely. Current theories include increased resistance to flow of CSF within the ventricular system or subarachnoid villi; intermittently elevated CSF pressure, usually at night; and ventricular enlargement caused by an initial rise in CSF pressure; the enlargement is maintained despite normal pressure because of the Laplace law. Although pressure is normal, the enlarged ventricular area reflects increased force on the ventricular wall.

Frequency

United States

Incidence of congenital hydrocephalus is 3 per 1,000 live births, while the incidence of acquired hydrocephalus is not known exactly.

International

Incidence of acquired hydrocephalus is unknown. About 100,000 shunts are implanted each year in the developed countries, but little information is available for other countries.

Mortality/Morbidity

In untreated hydrocephalus, death may occur by tonsillar herniation secondary to raised ICP with compression of the brain stem and subsequent respiratory arrest.

• Shunt dependence occurs in 75% of all cases of treated hydrocephalus and in 50% of children with communicating hydrocephalus.
• Patients are hospitalized for scheduled shunt revisions or for treatment of shunt complications or shunt failure.
• Poor development of cognitive function in infants and children, or loss of cognitive function in adults, can complicate untreated hydrocephalus. It may persist after treatment.
• Visual loss can complicate untreated hydrocephalus and may persist after treatment.

Sex

Generally, incidence is equal in males and females. The exception is Bickers-Adams syndrome, an X-linked hydrocephalus transmitted by females and manifested in males. NPH has a slight male preponderance.

Age

Incidence of human hydrocephalus presents a bimodal age curve. One peak occurs in infancy and is related to the various forms of congenital malformations. Another peak occurs in adulthood, mostly resulting from NPH. Adult hydrocephalus represents approximately 40% of total cases of hydrocephalus.

More on Hydrocephalus

Common Causes of Hydrocephalus

Although rare, hydrocephalus can be inherited genetically or may be associated with developmental disorders, including spina bifida (congenital defect of the spine) and encephalocele (hernia of the brain). Other causes can include bleeding within the brain, brain tumors, head injuries, complications of premature birth such as hemorrhage, or diseases such as meningitis or other infections. In some cases, normal flow of CSF within the brain is blocked, resulting in fluid build-up.

Symptoms of hydrocephalus vary greatly from person to person. According to the Hydrocephalus Association, some of the most common symptoms are listed below as a reference.

Symptoms of Hydrocephalus in infants Abnormal enlargement of the head; soft spot (fontanel) is tense and bulging; scalp can appear thin; bones separated in baby's head; prominent scalp veins; vomiting; drowsiness; irritability; downward deviation of baby's eyes; seizures; or poor appetite.

Symptoms of Hydrocephalus in toddlers/children
Abnormal enlargement of baby's head; headache; nausea; vomiting; fever; blurred or double vision; unstable balance; irritability; sleepiness; delayed progress in walking or talking; poor coordination; change in personality; inability to concentrate; loss of sensory motor functions; seizures; or poor appetite. Older children may experience difficulty in remaining awake or waking up.

Symptoms of Hydrocephalus in young and middle-aged adults
Headache; difficulty in remaining awake or waking up; loss of coordination or balance; bladder control problems; impaired vision and cognitive skills that may affect job performance and personal skills.

Symptoms of Hydrocephalus in older adults
Loss of coordination or balance; shuffling gait, memory loss; headache; or bladder control problems. Hydrocephalus is often categorized for age groups as either congenital or normal pressure hydrocephalus. Congenital hydrocephalus refers to conditions that are caused by conditions existing at birth. Primary symptoms include headache, nausea, vomiting and drowsiness. Normal pressure hydrocephalus (NPH) is the accumulation of cerebrospinal fluid that causes the ventricles in the brain to become enlarged, with little or no increase in pressure. Adult-onset NPH mainly occurs in adults age 60 and older. Patients with NPH often get misdiagnosed with Alzheimer's disease or dementia, as some of the symptoms mimic these two conditions.

Diagnosing Hydrocephalus

Before your doctor can recommend a course of treatment, he or she will:

• Review your medical history, and perform a physical examination
• Perform a complete neurological examination including diagnostic testing if needed
• Ask specific questions to determine if symptoms are caused by hydrocephalus

The neurological examination will also help to determine the severity of your condition. Further tests such as an ultrasound (if the patient is an infant), computed tomography (CT or CAT scan), or magnetic resonance imaging (MRI) may be ordered. The tests may reveal useful information about the severity of the condition and its likely cause.

When Surgery is Necessary

Hydrocephalus can be treated in a variety of ways. The problem area may be treated directly (by removing the cause of CSF obstruction), or indirectly (by diverting the fluid to somewhere else; typically to another body cavity). Indirect treatment is performed by implanting a device known as a shunt to divert the excess CSF away from the brain. The body cavity in which the CSF is diverted is usually the peritoneal cavity (the area surrounding the abdominal organs).

In some cases, two procedures are performed, one to divert the CSF, and another at a later stage to remove the cause of obstruction (e.g., a brain tumor). Once inserted, the shunt system usually remains in place for the duration of a patient's life (although additional operations to revise the shunt system are sometimes needed). The shunt system continuously performs its function of diverting the CSF away from the brain, thereby keeping the intracranial pressure within normal limits.

An alternative operation called endoscopic third ventriculostomy utilizes a tiny camera to look inside the ventricles, allowing the surgeon to create a new pathway through which CSF can flow.

Recovery

Your neurological function will be evaluated post surgery. If any neurological problems persist, rehabilitation may be required to further your improvement. However, recovery may be limited by the extent of the damage already caused by the hydrocephalus and by your brain's ability to heal.

Because hydrocephalus is an ongoing condition, long-term follow-up by a doctor is required. Follow-up diagnostic tests including CT scans, MRIs and x-rays, are helpful in determining if the shunt is working properly. Do not hesitate to contact your physician if you experience any of the following postoperative symptoms:

• Redness, tenderness, pain or swelling of the skin along the length of the tube or incision
• Irritability or drowsiness
• Nausea, vomiting, headache or double vision
• Fever
• Abdominal pain
• Return of preoperative neurological symptoms

Prognosis

The prognosis for hydrocephalus depends on the cause, the extent of symptoms, and the timeliness of diagnosis and treatment. Some patients show a dramatic improvement with treatment while others do not. In some instances of NPH, dementia can be reversed by shunt placement. Other symptoms such as headaches may disappear almost immediately if the symptoms are related to elevated pressure.

In general, the earlier hydrocephalus is diagnosed, the better the chance for successful treatment. The longer the symptoms have been present, the less likely it is that treatment will be successful. Unfortunately, there is no way to accurately predict how successful surgery will be for each individual. Some patients will improve dramatically while others will reach a plateau or decline after a few months.

Shunt malfunction or failure may occur. The valve can become clogged or the pressure in the shunt may not match the needs of the patient, requiring additional surgery. In the event of an infection, antibiotic therapy may be needed. A shunt malfunction may be indicated by headaches, vision problems, irritability, fatigue, personality change, loss of coordination, difficulty in waking up or staying awake, a return of walking difficulties, mild dementia or incontinence. Fortunately, most complications can be dealt with successfully.

Source: NeurosurgeryToday.Org