Hydrocephalus can be defined broadly as a disturbance of formation, flow, or absorption of cerebrospinal fluid (CSF) that leads to an increase in volume occupied by this fluid in the CNS. This condition also could be termed a hydrodynamic disorder of CSF. Acute hydrocephalus occurs over days, subacute hydrocephalus occurs over weeks, and chronic hydrocephalus occurs over months or years. Conditions such as cerebral atrophy and focal destructive lesions also lead to an abnormal increase of CSF in CNS.
Intracranial pressure (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 trans ventricular 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).
Clinical features of hydrocephalus are influenced by the following:
- Patient’s age
- Location of obstruction
- Rapidity of onset
Symptoms in infants
- Poor feeding
- Reduced activity
Symptoms in children
- Slowing of mental capacity
- Headaches (initially in the morning) that are more significant than in infants because of skull rigidity
- Neck pain suggesting tonsillar herniation
- Vomiting, more significant in the morning
- Blurred vision: This is a consequence of papilledema and later of optic atrophy
- Double vision: This is related to unilateral or bilateral sixth nerve palsy
- Stunted growth and sexual maturation from third ventricle dilatation: This can lead to obesity and to precocious puberty or delayed onset of puberty
- Difficulty in walking secondary to spasticity: This affects the lower limbs preferentially because the periventricular pyramidal tract is stretched by the hydrocephalus
Symptoms in adults
- Cognitive deterioration: This can be confused with other types of dementia in the elderly
- Headaches: These are more prominent in the morning because cerebrospinal fluid (CSF) is resorbed less efficiently in the recumbent position. This can be relieved by sitting up. As the condition progresses, headaches become severe and continuous. Headache is rarely if ever present in normal pressure hydrocephalus (NPH)
- Neck pain: If present, neck pain may indicate protrusion of cerebellar tonsils into the foramen magnum
- Nausea that is not exacerbated by head movements
- Vomiting: Sometimes explosive, vomiting is more significant in the morning
- Blurred vision (and episodes of “graying out”): These may suggest serious optic nerve compromise, which should be treated as an emergency.
- Double vision (horizontal diplopia) from sixth nerve palsy
- Difficulty in walking
- Incontinence (urinary first, fecal later if condition remains untreated): This indicates significant destruction of frontal lobes and advanced disease
Medical treatment in hydrocephalus is used to delay surgical intervention. It may be tried in premature infants with post hemorrhagic hydrocephalus (in the absence of acute hydrocephalus). Normal CSF absorption may resume spontaneously during this interim period.
Surgical treatment is the preferred therapeutic option. Repeat lumbar punctures (LPs) can be performed for cases of hydrocephalus after intraventricular hemorrhage, since this condition can resolve spontaneously. If reabsorption does not resume when the protein content of cerebrospinal fluid (CSF) is less than 100 mg/dL, spontaneous resorption is unlikely to occur. LPs can be performed only in cases of communicating hydrocephalus.
Alternatives to shunting include the following:
- Choroid plexectomy or choroid plexus coagulation may be effective.
- Opening of a stenosed aqueduct has a higher morbidity rate and a lower success rate than shunting, except in the case of tumors. However, lately cerebral aqueductoplasty has gained popularity as an effective treatment for membranous and short-segment stenoses of the sylvian aqueduct. It can be performed through a coronal approach or endoscopically through sub occipital foramen magnum trans-fourth ventricle approach. In these cases, tumor removal cures the hydrocephalus in 80%.
- Endoscopic fenestration of the floor of the third ventricle establishes an alternative route for CSF toward the subarachnoid space. It is contraindicated in communicating hydrocephalus.
Shunts eventually are performed in most patients. The principle of shunting is to establish a communication between the CSF (ventricular or lumbar) and a drainage cavity (peritoneum, right atrium, pleura). Remember that shunts are not perfect and that all alternatives to shunting should be considered first.
- A ventriculoperitoneal (VP) shunt is used most commonly. The lateral ventricle is the usual proximal location. The advantage of this shunt is that the need to lengthen the catheter with growth may be obviated by using a long peritoneal catheter.
- A ventriculoatrial (VA) shunt also is called a “vascular shunt.” It shunts the cerebral ventricles through the jugular vein and superior vena cava into the right cardiac atrium. It is used when the patient has abdominal abnormalities (e.g., peritonitis, morbid obesity, or after extensive abdominal surgery). This shunt requires repeated lengthening in a growing child.
- A lumboperitoneal shunt is used only for communicating hydrocephalus, CSF fistula, or pseudotumor cerebri.
- A Torkildsen shunt is used rarely. It shunts the ventricle to cisternal space and is effective only in acquired obstructive hydrocephalus.
- A ventriculopleural shunt is considered second line. It is used if other shunt types are contraindicated.