الثلاثاء، 21 أغسطس 2012

Hydrocephalus


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.[1] 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. In these situations, loss of cerebral tissue leaves a vacant space that is filled passively with CSF. Such conditions are not the result of a hydrodynamic disorder and therefore are not classified as hydrocephalus. An older misnomer used to describe these conditions was hydrocephalus ex vacuo.
Normal pressure hydrocephalus (NPH) describes a condition that rarely occurs in patients younger than 60 years.[2] Enlarged ventricles and normal CSF pressure at lumbar puncture (LP) in the absence of papilledema led to the term NPH. However, intermittent intracranial hypertension has been noted during monitoring of patients in whom NPH is suspected, usually at night. The classic Hakim triad of symptoms includes gait apraxia, incontinence, and dementia. Headache is not a typical symptom in NPH.
Benign external hydrocephalus is a self-limiting absorption deficiency of infancy and early childhood with raised intracranial pressure (ICP) and enlarged subarachnoid spaces. The ventricles usually are not enlarged significantly, and resolution within 1 year is the rule.
Communicating hydrocephalus occurs when full communication occurs between the ventricles and subarachnoid space. It is caused by overproduction of CSF (rarely), defective absorption of CSF (most often), or venous drainage insufficiency (occasionally).
Communicating hydrocephalus with surrounding "atroCommunicating hydrocephalus with surrounding "atrophy" and increased periventricular and deep white matter signal on fluid-attenuated inversion recovery (FLAIR) sequences. Note that apical cuts (lower row) do not show enlargement of the sulci, as is expected in generalized atrophy. Pathological evaluation of this brain demonstrated hydrocephalus with no microvascular pathology corresponding with the signal abnormality (which likely reflects transependymal exudate) and normal brain weight (indicating that the sulci enlargement was due to increased subarachnoid cerebrospinal fluid [CSF] conveying a pseudoatrophic brain pattern). Noncommunicating hydrocephalus occurs when CSF flow is obstructed within the ventricular system or in its outlets to the arachnoid space, resulting in impairment of the CSF from the ventricular to the subarachnoid space. The most common form of noncommunicating hydrocephalus is obstructive and is caused by intraventricular or extraventricular mass-occupying lesions that disrupt the ventricular anatomy.[3]
Noncommunicating obstructive hydrocephalus caused Noncommunicating obstructive hydrocephalus caused by obstruction of the foramina of Luschka and Magendie. This MRI sagittal image demonstrates dilatation of lateral ventricles with stretching of corpus callosum and dilatation of the fourth ventricle. Noncommunicating obstructive hydrocephalus caused Noncommunicating obstructive hydrocephalus caused by obstruction of foramina of Luschka and Magendie. This MRI axial image demonstrates dilatation of the lateral ventricles. Noncommunicating obstructive hydrocephalus caused Noncommunicating obstructive hydrocephalus caused by obstruction of foramina of Luschka and Magendie. This MRI axial image demonstrates fourth ventricle dilatation. Congenital hydrocephalus applies to the ventriculomegaly that develops in the fetal and infancy periods, often associated with macrocephaly.[4] The most common causes of congenital hydrocephalus are obstruction of the cerebral aqueduct flow, Arnold-Chiari malformation or Dandy–Walker malformation.[5] these patients may stabilize in later years due to compensatory mechanisms but may decompensate, especially following minor head injuries. During these decompensations, determining the extent to which any new neurological deficits may be due to the new acute event, compared with hydrocephalus that may have gone unnoticed for many years, is difficult.


Hydrocephalus Signs and Symptoms

Symptoms of hydrocephalus are determined by the following factors:
  • Age
  • Degree of ventricular enlargement
  • Rate of hydrocephalus development
  • Type
  • Underlying condition

Symptoms of Hydrocephalus in Infants

The characteristic symptom seen in infants is enlargement of the head. An infant's skull expands to accommodate excess CSF because the bones of the skull have not closed yet.
Very young children commonly experience irritability, poor feeding, and lethargy.

Symptoms of Hydrocephalus in Children and Adults

Children and adults may experience the following symptoms:
  • Blurred or double vision
  • Cognitive difficulties
  • Downward gaze or "sun-setting eyes"
  • Headache
  • Imbalance and dizziness
  • Incontinence
  • Irregular gait
  • Lethargy
  • Nausea
  • Poor coordination
  • Visual disturbances
  • Vomiting
  • Weakness



Diagnosis of Hydrocephalus

If you think that you or someone you care about may have hydrocephalus, we recommend you learn about the symptoms and diagnostic tests for this condition. We also encourage you to trust your instincts. If you notice changes or have an intuitive feeling that something is not right with the person you are concerned about, act on that feeling and seek medical attention.
Only a medical doctor can make a diagnosis of hydrocephalus. The information here is intended to help you understand and navigate through the process of seeking medical advice. In children, it is often a pediatrician who first suspects hydrocephalus. A pediatric neurosurgeon will typically make the final diagnosis. In adults, hydrocephalus is often diagnosed by a neurologist working with a neurosurgeon.
If you have already received a diagnosis, the information below will help you make sense of the classifications and causes of hydrocephalus.

Symptoms and Diagnostic Tests

Symptoms of untreated hydrocephalus are variable. During pregnancy, routine ultrasound can detect enlarged ventricles (spaces) within the baby’s brain. In children the symptoms tend to be related to high pressure and may include nausea, vomiting, headache and vision problems. In young and middle aged adults symptoms run the gamut of those seen in children and in older adults and most often include dizziness and vision problems. In older adults with NPH the symptoms are more likely to be loss of function in three main areas: walking, thinking and bladder control.
Infants and Children Young & Middle Aged Adults Older Adults (NPH)
Abnormal Head Enlargement Difficulty Walking Difficulty Walking
Tense, Bulging Fontanel Cognitive Challenges Cognitive Challenges
Prominent Scalp Veins Urinary Urgency or Incontinence Urinary Urgency or Incontinence
Skull bones may feel seperated Chronic Headaches
Vomiting, Sleepiness, Irritability
Headache, Nausea, Vomiting, Vision
Downward Deviation of Eyes
The most common initial diagnostic test to determine hydrocephalus at any age is an image of the brain (CT Scan or MRI) to identify the enlarged ventricles (spaces) within the brain that are typical of hydrocephalus. More tests are often performed in adults. The following links take you to detailed information about the signs, symptoms and diagnostic tests for hydrocephalus in various age groups.


Acute hydrocephalus treatment

For initial treatment of acute hydrocephalus one will initially use medicines which reduce CSF production, and lumbar punctures. Mesurements of inter-cranial pressure, and the various scanning techniques are used to asses the further treatment.
If the CSF pressure does not return to normal other methods may be used to release the pressure such as "ventricular taps" where the CSF is drained dirrectly from the ventricule.
After some time it will become clear wether the increase in pressure has stopped, or has become continuous and requires surgical treatment.

Treating the causes

Treatment of the causative factors is the best strategy. When the ventricles are enlarged one needs to determine the cause. In the case of obstructive hydrocephalus, an unequal enlargement of the ventricles will point to the location of the obstruction. Causative factors for the obstruction are then searched for. Tumours or blood clots can obstruct the CSF pathways, and their removal can often re-establish a normal CSF flow pathway. Obstruction at the aqueduct or the outlets of the fourth ventricle can often be treated by surgically creating a new outlet for the ventricles, through the floor of the third ventricle (third ventriculostomy). Blockage of the foramen of Monroe with a resultant trapped lateral ventricle can be treated by surgically creating a window through the curtain of tissue separating the two lateral ventricles (septal fenestration).
Endoscopy operations involve inserting a small endoscope into the ventricle through a single small hole in the skull. The endoscope is connected via a micro-camera to a television monitor on which the surgeon can see inside the ventricles. Using these endoscopes, neurosurgeons can now create a bypass, allowing CSF to flow around certain blockages and restoring normal flow. Only certain patients are eligible for endoscopic surgery, and the patients must be selected carefully. In particular, patients with blockages within the ventricles themselves (those with obstructive hydrocephalus) are potentially candidates for endoscopic surgery.
When the CT or MRI scans show a case of hydrocephalus which cannot be dealt with using one of the above techniques, a permanent device needs to be surgically implanted to draw the fluid out of the ventricles and to carry it to some other cavity within the body where it will be reabsorbed into the blood stream. Such devices are called shunts and they became practical in the 1950's when common problems with hydrocephalus treatments were being solved. These consisted of rejection of the tubing by the body's defences, as well as infections and blockages of the tube. 



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