hydrocephalus

HYDROCEPHALUS (HCP)

for 5th class: medical college: Al Mustansiriyah University
by Dr Mohamed Al Tamimi

DEFINITION:

increased CSF volume: normal CSF volume = 100 - 150 mL (50 in ventricles, 25 around brain,75 around spinal cord)
CSF production is constant at 35 cc/hr (500 - 750 cc/day)

MECHANISMS

increased production e.g. choroid plexus papilloma (0.4-1% of intracranial tumours)
decreased absorption (see below)

CLASSIFICATION

Non-Communicating (Obstructive) Hydrocephalus
absorption is blocked within ventricular system - no escape of CSF into subarachnoid space
causes/location of block
• intraventricular hemorrhage
• ventricular tumours (e.g. 3rd ventricle colloid cyst)
• supratentorial mass causing tentorial herniation and aqueduct compression
• infratentorial mass causing 4th ventricle obstruction or aqueduct kinking
• congenital e.g. aqueductal stenosis
CT findings
• lateral and 3rd ventricles dilated
• normal 4th ventricle (e.g. aqueduct stenosis) or deviated/absent 4th ventricle (e.g. posterior fossa mass)


Communicating (Non-Obstructive) Hydrocephalus
absorption is blocked at some part of extraventricular pathway, such as arachnoid granulations
causes
• meningitis
• SAH
• trauma
CT findings
all ventricles are dilated

Normal Pressure Hydrocephalus (NPH)

gradual onset of classic triad ( gait apraxia, incontinence, dementia)
CSF pressure often within clinically “normal” range
usually communicating in nature

Hydrocephalus Ex Vacuo

enlargement of ventricles (and sulci) secondary to diffuse brain atrophy
usually a function of normal aging
not true hydrocephalus
CLINICAL FEATURES OF HYDROCEPHALUS
Acute HCP
signs and symptoms of acute raised ICP
usually non-communicating type
Chronic HCP
similar to NPH


INVESTIGATIONS
1. CT
ventricular enlargement, may see prominent temporal horns
periventricular lucency (CSF forced into extracellular space)
narrow/absent sulci, +/– 4th ventricular enlargement
2. Ultrasound (through anterior fontanelle in infants)
ventricular enlargement

MANAGEMENT

1. spinal taps (for transient, communicating HCP)
2. remove obstruction (if possible)
3. choroid plexectomy (for choroid plexus papilloma)
4. third ventriculostomy (for obstructive HCP)
5. shunts
• ventriculoperitoneal (VP) = ventricle to peritoneum
• ventriculo-atrial (VA) = ventricle to right atrium
• lumboperitoneal = lumbar spine to peritoneum (for communicating HCP)

Shunt Complications

1. obstruction
• etiology: infection, obstruction by choroid plexus, buildup of proteinaceous accretions, blood, cells (inflammatory or tumor)
• signs and symptoms of acute HCP or increased ICP
• radiographic evaluation: “shunt series” (plain x-rays which only show disconnection of tube system), CT
2. infection (3-4%)
• etiology: S. epidermidis, S. aureus, gram-negative bacilli
• presentation: fever, nausea and vomiting, anorexia, irritability; signs and symptoms of shunt obstruction; shunt nephritis (antibodies generated against bacteria in shunt leads to kidney damage)
• investigation: CBC, blood culture, shunt tap (LP usually NOT recommended)
3. overshunting
• slit ventricle syndrome (collapse of ventricles leading to shunt catheter occlusion by ependymal lining)
• subdural effusion
• secondary craniosynostosis (children)
• low pressure headache
4. seizures
5. problems related to distal catheter (blockage)