Hydrocephalus


Hydrocephalus is a condition in which cerebrospinal fluid builds up within and/or around the brain, which can cause pressure to increase in the skull. Symptoms may vary according to age. Headaches and double vision are common. Elderly adults with normal pressure hydrocephalus may have poor balance, difficulty controlling urination or mental impairment. In babies, there may be a rapid increase in head size. Other symptoms may include vomiting, sleepiness, seizures, and downward pointing of the eyes.
Hydrocephalus can occur due to birth defects or can develop later in life. Hydrocephalus can be classified via mechanism into communicating, noncommunicating, ex vacuo, and normal pressure hydrocephalus. Diagnosis is made by physical examination and medical imaging, such as a CT scan.
Hydrocephalus is typically treated through surgery. One option is the placement of a shunt system. A procedure called an endoscopic third ventriculostomy has gained popularity in recent decades, and is an option in certain populations. Outcomes are variable, but many people with shunts live normal lives. However, there are many potential complications, including infection or breakage. There is a high risk of shunt failure in children especially. However, without treatment, permanent disability or death may occur.
Hydrocephalus affects about 0.1–0.6% of newborns. Rates in the developing world may be higher. Normal pressure hydrocephalus affects about 6% of patients over 80. Description of hydrocephalus by Hippocrates dates back more than 2,000 years. The word hydrocephalus is from the Greek, meaning 'water' and, meaning 'head'.

Signs and symptoms

The clinical presentation of hydrocephalus varies with age as well as chronicity.

Infants

Hydrocephalus is difficult to detect clinically before delivery, although enlarged ventricles can be spotted on ultrasonography as early as 18–20 weeks gestation. Since infants' skulls are not fully fused together at the cranial sutures yet, they have soft spots on their skulls known as open fontanelles. This anatomic characteristic means that infants' skulls can visibly grow in size when cerebrospinal fluid accumulates. Therefore, infants with hydrocephalus may present with an enlarged skull, bulging fontanelles, or separated cranial sutures. Parents or physicians may also note that the infant is more irritable or tired than normal. Other symptoms include seizures, inability to look upwards, and pauses in breathing. Infants may also present with lack of weight gain or failure to meet motor and developmental milestones. Imaging can be done to confirm the suspected diagnosis of hydrocephalus. In infants, the open fontanelles allow for use of head ultrasonography. This allows pediatricians to minimize radiation exposure and come up with a diagnosis quickly. If further information is needed, an MRI can be done.
Of note, hydrocephalus in infants can occur as part of a syndrome, and therefore patients may present with other characteristic symptoms. An example of one such syndrome is the Walker-Warburg syndrome, in which patients may also have holoprosencephaly and several other cranial defects. The VACTERL disorders may also include hydrocephalus, and can then be called VACTERL-H. Hydrocephalus can also occur as part of neurocutaneous disorders such as neurofibromatosis type I and tuberous sclerosis. Lastly, patients with trisomy disorders as well as triploidy have been noted to have hydrocephalus.

Children

In older children, the fontanelles are closed, so there is no visible change in head size. Since there is limited expansion of the skull, symptoms are more representative of the effects of increased intracranial pressure on a child's developing brain. The most common presenting features in this age group are memory and concentration issues as well as motor and gait abnormalities. Nausea, vomiting, and a tremor of the arms and legs are also common features in older children. Patients may also have papilledema, worsening vision, and difficulty looking upwards on examination. A key feature in this age group includes headaches, due to the intracranial hypertension caused by the increased CSF in the closed space of the skull. These headaches tend to occur early in the morning as patients have been in a horizontal position throughout the night, which increases ICP.
Symptoms that may occur in older children can include:
  • Brief, shrill, high-pitched cry
  • Changes in personality, memory, or the ability to reason or think
  • Changes in facial appearance and eye spacing
  • Crossed eyes or uncontrolled eye movements
  • Difficulty feeding
  • Excessive sleepiness
  • Headaches
  • Irritability, poor temper control
  • Loss of bladder control
  • Loss of coordination and trouble walking
  • Muscle spasticity
  • Slow growth
  • Delayed milestones
  • Failure to thrive
  • Slow or restricted movement
  • Vomiting
Since increased intracranial pressure can damage the brain, thought and behavior may be negatively affected. Learning disabilities, including short-term memory loss, are common among those with hydrocephalus. Affected children tend to score better on verbal IQ than on performance IQ, a pattern which is thought to reflect the distribution of nerve damage to the brain. Hydrocephalus that is present from a young age can cause long-term problems with speech and language. Children can have trouble understanding complex and abstract concepts or difficulty retrieving stored information. They may also have a nonverbal learning disorder or spatial/perceptual disorders. Children affected by hydrocephalus may also have difficulty in understanding concepts within conversation. This is thought to be due to an inability to understand or interpret context. These children may tend to use words they know or have heard. However, the severity of hydrocephalus can differ considerably between individuals, and some are of average or above-average intelligence. Aside from learning disabilities, a child with hydrocephalus may also have coordination and visual problems. They may reach puberty earlier than the average child. About one in four develops epilepsy.

Adults

In adults, acute hydrocephalus can have many of the same signs and symptoms of increased intracranial pressure that are seen in children. Increased volumes of CSF can also result in hearing loss, including sensorineural hearing loss. Hearing loss is a rare but well-known sequela of procedures resulting in CSF loss. Elevated ICP can also cause a portion of the brain to move out of place, which can result in brain stem compression and possibly death.
By contrast, chronic dilatation may present in a more insidious manner. Hakim's triad of gait instability, urinary incontinence, and dementia is a relatively typical manifestation of a form of hydrocephalus known as normal pressure hydrocephalus. Focal neurological deficits may also occur, such as abducens nerve palsy and vertical gaze palsy. The symptoms depend on the cause of the blockage, the person's age, and how much brain tissue has been damaged by the swelling.
Hydrocephalus ex vacuo is a condition in which there is ventriculomegaly due to loss of brain volume which then results in a subsequent increase in CSF. This is most commonly seen in patients with neurodegenerative disorders such as Alzheimer's disease. Therefore, the presenting symptoms of this condition will likely be those of Alzheimer's: memory loss, loss of language skills or comprehension, inability to perform purposeful movements, and inability to conduct activities of daily living independently. Hydrocephalus ex vacuo can also occur due to traumatic brain injuries or due to strokes.

Causes

Hydrocephalus can be caused by a combination of factors and is not fully understood. Any medical condition that interrupts the flow of cerebrospinal fluid can cause this build-up of excess fluid. This occurs due to blocked pathways of cerebrospinal fluid, issues with CSF reabsorption, or increased CSF production.
Hydrocephalus can be classified as primary or secondary based on the cause.

Primary

Primary hydrocephalus involves congenital, developmental, and genetic factors that lead to excess CSF build-up. Up to 50% of the causes of primary hydrocephalus are genetic.
Congenital hydrocephalus is defined by the presence of excess CSF at birth. It occurs due to a combination of factors, especially genetic causes prior to birth. The genes involved in congenital hydrocephalus involve aqueduct defects, development of the central nervous system, and cilia. The most common cause of congenital hydrocephalus is aqueductal stenosis, which occurs when the narrow passage between the third and fourth ventricles in the brain is blocked or too narrow to allow sufficient cerebral spinal fluid to drain. Fluid accumulates in the upper ventricles, causing build up and hydrocephalus.
Developmental disorders including neural-tube defects, arachnoid cysts, Dandy–Walker malformations, and Arnold–Chiari malformations can cause primary hydrocephalus. Dandy-walker malformations and Arnold-Chiari malformations lead to structural abnormalities in the brain, which disrupts the flow of CSF and causes hydrocephalus.
Neural tube defects are commonly caused by a deficiency of folic acid during pregnancy. Spina bifida is a neural tube defect that involves defects in the development of the spine, and it can cause hydrocephalus. Myelomeningocele is the most severe type of spina bifida, involving an open spinal column and the exact mechanism of hydrocephalus involved in this condition is unclear.

Secondary (Acquired)

Secondary hydrocephalus is acquired as a consequence of CNS infections, meningitis, brain tumors, head trauma, toxoplasmosis, or intracranial hemorrhage.
Intraventricular hemorrhage, or bleeding within the ventricles of the brain, leads to hydrocephalus in 51–89% of patients. This is because the blood in the ventricles blocks the regular flow of CSF, leading to build-up of excess CSFFile:Intracerebral hemorrhage.jpg|thumb|upright=1.2|Spontaneous intracerebral and intraventricular hemorrhage with hydrocephalus shown on CT scanNormal pressure hydrocephalus most often occurs in elderly patients with symptoms including gait disturbance, urinary incontinence, and cognitive issues. It is commonly divided into two categories, idiopathic NPH and secondary NPH.
Hydrocephalus can also be caused by overproduction of CSF such as choroid plexus papilloma, villous hypertrophy.
Brain atrophy or breakdown in elderly patients or patients with conditions like Parkinson's or Alzheimer's can lead to acquired hydrocephalus. This is likely because the breakdown of brain cells leads to ventriculomegaly and increased space for CSF to fill.