Chapter 6-The Ventricles, Choroid Plexus, and Cerebrospinal Fluid

Extraventricular obstruction may occur at any place in the subarachnoid space but is more common around the:

1) Base of brain 2) Tentorium cerebelli 3) Tentorial notch 4) Over the convexity of the hemisphere 5) Superior sagittal sinus

Occlusion of the cerebral aqueduct during development may be the result of:

1) Glial scarring (gliosis) due to infection 2) Consequence of developmental defects of the forebrain 3) Rupture of the amnionic sac in utero 4) Forking of the aqueduct

A variety of events may result in blood accumulating in the ventricular spaces in the brain:

1) Hemorrhage into the substance of the brain (such as cerebral hemorrhage) that subsequently ruptures into the ventricular space 2) Rupture of an intracranial aneurysm (especially those located immediately adjacent to the third or fourth ventricles) 3) Severe head trauma (there may be blood in the subarachnoid space and/or in the substance of the brain depending on the degree of injury

Common intraventricular sites of potential obstruction are:

1) Interventricular foramen 2) Cerebral aqueduct 3) Caudal portions of the fourth ventricle 4) Foramen of fourth ventricle

CSF) In syphilitic meningitis,

200 to 300 cells/mL would be typical, and most of these would be lymphocytes

Lumbar puncture is used to collect a sample of CSF for analysis and to measure CSF pressure

A needle is inserted between the third and fourth (or fourth and fifth) lumbar vertebrae into the dural sac, the spinal fluid pressure is measured, and a few milliliters of fluid is withdrawn • Because the average volume of CSF in the adult is about 120 mL/day, and the rate of production is about 450 to 500mL/day, the sample removed is quickly replaced

Normal Pressure Hydrocephalus (Part 2)

Cause is unclear In some patients, the combination of a difficult shuffling gait and dementia may mimic the clinical picture in degenerative disease such as Alzheimer and Parkinson diseases Treatment is a shunting procedure to reduce CSF pressure and volume; in some cases there is general clinical improvement with lessening of all symptoms including those related to mental status

Ependymomas (Part 1)

Constitutes 5% to 6% of all glial cell neoplasms, originates from the ependymal cells lining the ventricles May appear in any ventricle, the majority (60% to 75%) are located in the spaces of the posterior fossa May also be found within the spinal cord or in the region of the cauda equina Seen most frequently in children younger than 5 years of age Histologic appearance of ependymomas may vary, even from place to place within the same tumor

Communicating Hydrocephalus (Part 1)

Flow of CSF through the ventricular system and into the subarachnoid space is not impaired Movement of CSF through the subarachnoid space and into the venous system is partially or totally blocked May be caused by a congenital absence (agenesis) of the arachnoid villi Villi may be partially blocked by red blood cells subsequent to a subarachnoid hemorrhage

Tumors of the Choroid Plexus (Part 3)

Histologically, these tumors are characterized by clusters of cuboidal or columnar cells that are strikingly similar to normal choroid plexus epithelium These cell clusters are insinuated between comparatively thin areas containing small vessels and loose connective tissue; this is an important difference between this tumor and an ependymoma, which has thick intervening areas that are composed of glial cell processes Mitotic figures are infrequently seen but when present may indicate that the tumor is malignant

Hemorrhage into the Ventricles (Part 1)

Less frequently, rupture or bleeding from an intraventricular arteriovenous malformation (AVM), or bleeding from a tumor located in, or invading, the ventricular space Blood in the ventricles, especially acute blood, is clearly seen on CT

Ependymomas (Part 2)

Location of ependymoma determines the symptoms experience by the patient Lesions in the supratentorial locations may produce signs and symptoms reflecting their location e.g. hydrocephalus in case of blocked CSF flow or seizure activity Lesions in the infratentorial locations frequently cause nausea and vomiting, headache, other signs and symptoms related to hydrocephalus, and cranial nerve signs and symptoms indicative of compression of, or tumor infiltration into, the brainstem

Aqueductal Stenosis

May be caused by a tumor in the immediate vicinity of the midbrain (pineoblastoma or meningioma) • May also be occluded by the cellular debris seen following: 1) Intraventricular hemorrhage 2) Bacterial or fungal infections 3) Ependymal proliferation due to viral infections of CNS (mumps)

Obstructive Hydrocephalus

May result from an obstruction somewhere within the ventricular system or within the subarachnoid space

Tumors of the Choroid Plexus (Part 2)

Patients present with signs and symptoms of increased intracranial pressure (headache, nausea, vomiting, lethargy), hydrocephalus (excessive production of CSF), or deficits of eye movement due to pressure on the roots of CN III, IV, or VI Treatment of choice for choroids plexus papilloma is surgical removal Choroid plexus carcinoma is treated more aggressively, first with chemotherapy, followed by surgery, then with a combination of chemotherapy and radiation

Hydrocephalus

The condition is usually caused by an obstruction of CSF flow with resultant enlargement of the ventricular spaces upstream to the blockage

When there is evidence of blood in the retrieved sample of CSF, it is important to establish if this observation is due to subarachnoid hemorrhage or due to damage to a vessel during the procedure: a traumatic tap

The three-tube test is performed to determine if the blood is due to subarachnoid hemorrhage or traumatic tap • Three successive tubes of CSF are drawn • If the first tube contain blood, the second little or none, and the third none, it was most likely a traumatic tap • If all three tubes contain bloody CSF that is also xanthochromic, it most likely means that there is bleeding into the subarachnoid space

Ependymomas (Part 4)

The tissue septa between cell rosettes are usually thick and contain layers of neuroglial cell process Treatment for patients with ependymoma is primarily with surgical removal followed by focal irradiation Incomplete removal, for example, in cases with tumor infiltration into the brainstem, reduces survival rates even with radiation therapy and chemotherapy

Hemorrhage into the Ventricles (Part 2)

The white appearance of the blood on CT characteristically outlines the ventricular spaces and is clearly distinguishable from blood at other intracranial locations Blood in the ventricular spaces can create an in vivo cast showing details of ventricular spaces and their relationships Alterations of size, shape, or position of a ventricle containing blood may be indicative of further neurologic complications

Hydrocephalus is characterized by

an increase in CSF volume, enlargement of one or more of the ventricles, and, usually, an increase in CSF pressure

CSF) Lymphocytes

are also the predominant cell type found in active multiple sclerosis, even though there are usually fewer than 50 cells/mL of CSF; the diagnosis of multiple sclerosis also rests on specific changes in the immunoglobulin G content of CSF and a slight increase in the number of mononuclear cells

Normal CSF is

clear and colorless and contains very little protein (15 to 45 mg/dL), little immunoglobulin, and only one to five cells (leukocytes) per milliliter; changes from these normal values are useful in diagnosis of a variety of disease processes

The cerebral aqueduct is a

constricted region in the ventricular system and is a point at which the flow of CSF may be easily blocked

A major sequela of aqueductal blockade is

enlargement of the third and both lateral ventricles (triventricular hydrocephalus)

Unilateral obstruction of one interventricular foramen,

for example by a colloid cyst, results in enlargement of the lateral ventricle on that side

Compared with blood plasma, CSF has

higher concentrations of chloride, magnesium, and sodium; similar concentrations of creatinine; and lower concentrations of potassium, calcium, glucose, proteins, albumin, and uric acid Deviation from these normal values is indicative of a pathologic state or ongoing pathologic process

The CSF of cancer patients

may also contain malignant cells characteristic of their primary lesions

CSF) In bacterial meningitis or brain abscesses,

neutrophils predominate and may reach concentrations of 1000 to 20,000/mL and the CSF is cloudy

Hydrocephalus

o Any condition (reabsorption failure, overproduction, or obstruction of movement through ventricular system) that causes CSF to accumulate in the ventricular spaces or around the brain produces neurological deficits such as hydrocephalus as seen in a fetus or in a newborn

CSF with bleeding

o In marked contrast to the elevated numbers of white blood cells seen in CNS infections, numerous red blood cells are present in the CSF of patients who have bleeding into the subarachnoid space e.g. may result from rupture of an intracranial aneurysm or arteriovenous malformation

CSF with subarachnoid hemorrhage

o Patients with subarachnoid hemorrhage or those with primary CNS tumors usually have elevated protein levels in their CSF; elevated CSF protein is also seen in patients with syphilis or meningitis and in cancer patients in whom the disease has metastasized into the CSF

Tumors of the Choroid Plexus (Part 1)

o Relatively rare, comprising somewhat less than 1% of all intracranial tumors o Lesions are classified as choroids plexus papillomas which are benign and the more frequently seen or as choroids plexus carcinomas which are malignant and rarely seen o May be seen in patients of any age but are more common between birth and 10 years of age o More often occur in the fourth ventricle (50% to 60%) but may also be found in the lateral ventricles

Ependymomas (Part 3)

o These tumors are generally characterized by clusters of various sizes that are composed of polygonal or columnar cells arranged in a circle facing a lumen (true rosettes); these configurations are made up of long cell processes impinging on a vessel with cell bodies and nuclei located somewhat distal to these processes o Less commonly seen are ependymal rosettes consisting of cell clusters surrounding lumina of varying sizes; cell apexes in these clusters may contain a basal body (blepharoplast) associated with the cilium of the ependymal cell o The blepharoplast is visualized with stains for glial fibrillary proteins; the presence of this basal body, in a stained section, is one feature that differentiates this tumor from a choroids papilloma

Blockage of both interventricular foramina will

produce enlargement of both lateral ventricles

Obstruction of the exit channels of the fourth ventricle,

the foramina of Magendie and Luschka, will result in enlargement of all parts of the ventricular system

Normal Pressure Hydrocephalus (Part 1)

• CSF is elevated episodically when measured over time • Affected patients are usually elderly • Although intracranial pressure may initially be elevated and the ventricles enlarged, the pressure may wax and wane over time or even subside to a high-normal level, however, the effects of the increased pressure remain • Patients with normal-pressure hydrocephalus experience a diagnostic triad consisting of urinary problems (frequency, urgency, or incontinence), impaired gait that is most obvious on stepping up as on a curb, and dementia

Idiopathic Intracranial Hypertension (pseudotumor cerebri)

• Enigmatic condition most commonly seen in obese women of child-bearing age and in persons with chronic renal failure • Possibly related to vitamin A toxicity • Increase in intracranial pressure (>25cm H2O), with little evidence of pressure increase on CT or MRI scans, such as ventricular enlargement or effacement of sulci or cisterns

Communicating Hydrocephalus (Part 2)

• High level of proteins in the CSF (above 500 mg/dL), as seen in patients with CNS tumors or inflammation • High CSF pressure is due partially to the sequestering of protein in the arachnoid villi and subsequent blockage of CSF transport into the venous system • Interruption of CSF movement through the subarachnoid space caused by either subarachnoid hemorrhage or a major CNS infection, such as leptomeningitis, and the subsequent inflammatory responses

Hydrocephalus ex Vacuo

• Not true hydrocephalus but generalized atrophy of the brain resulting in ventricles that are relatively larger owing to the loss of white matter • No increase in intracranial pressure • No neurologic deficits other than those that may be related to brain atrophy and treatment is not indicated • May also refer to atrophy with a change in ventricular size that may follow, by several years, an event such as a stroke

Communicating Hydrocephalus (Part 3)

• Overproduction of CSF in patients with papilloma of the choroid plexus may also be a factor • In all of these situations there is an enlargement of all parts of the ventricular system • Although rare, hydrocephalus may also be seen in patients with impaired venous flow from the brain

(Pseudotumor cerebri) Idiopathic Intracranial Hypertension

• Patients usually experience headache and a variety of visual deficits (up to blindness) due to papilledema (swelling of the optic disc) • Treatments include a program of weight loss, medication, and if needed, shunting (lumboperitoneal) or surgical fenestration, which consists of making a window in the optic sheath to relieve pressure on the optic nerve