CSF System Flashcards
Hydrocephalus
Recognized as enlarged ventricles out of proportion to the amount of cerebral atrophy
Communicating Hydrocephalus
Occurs when the ventricular system is in continuity with the SAS and all the ventricles are enlarged, including the fourth ventricle. In nearly all cases, it results from impaired CSF absorption. Rarely, hydrocephalus occurs from excess CSF production.
Normal Pressure Hydrocephalus (a type of communicating hydrocephalus)
The opening pressure is within normal range, but too high for the size of the ventricles.
Presents with a classic triad: impaired gait, urinary incontinence and mental status changes. It’s important as it’s potentially treatable by shunting
LaPlace’s Law
Wall tension (force) is proportional to both pressure and radius; thus if the ventricles are enlarged (increased radius) even in the setting of normal pressure, then the wall tension is increased resulting in compression of adjacent brain structures
Non-communicating Hydrocephalus (example-acute bleed into a cerebellar tumor)
In the example, there’s acute blood in the vermis of the cerebellum. Looking closely, one sees that the cerebellum is enlarged by a mass which compresses the fourth ventricle. This is an acute bleed into a tumor, compressing the fourth ventricle, which resulted in acute non-communicating hydrocephalus. Note there is dilated temporal horns, mildly enlarged lateral and third ventricles as well as the complete absence of sulci over the convexities. Surgical decompression of the cerebellar mass showed a malignant ependyoma
Non-communicating hydrocephalus (definition)
Occurs when the ventricular system is not in continuity with the SAS. Most often, the site of blockage in non-communicating hydrocephalus is the cerebral aqueduct, but rarely can occur at the foreman of Monro, the third ventricle or the outlet of the fourth ventricle. Acute, non-compensated, non-communicating hydrocephalus is a neurosurgical emergency as the non-compensated hydrocephalus results in a progressive increase in ICP, which if left unchecked will result in herniation and brain death. Potentially treatable by shunting
Non-communicating hydrocephalus-acute shunt malfunction
Note the prominent enlargement of the lateral and third ventricles in the setting of a normal sized fourth ventricle. This pattern is one of non-communicating hydrocephalus, which occurs from impaired drainage through the cerebral aqueduct which connects the third and fourth ventricles. This picture differs from communicating hydrocephalus wherein all the ventricles are enlarged. Shunt malfunction is a common cause of acute hydrocephalus, which requires immediate neurosurgical intervention to reduce pressure.
Acute Hydrocephalus from Cerebellar Stroke (Non communicating)
Note the hypodensity in the right cerebellum denoting the subacute stroke. In ischemic stroke, maximal edema typically occurs on day 2 or 3. In this case, one can see that the stroke has swelled and compressed the fourth ventricle, resulting in acute non-communicating hydrocephalus. The third ventricle which normally has the shape of a slit has now become round. The temporal horns of the lateral ventricles have also become markedly enlarged. Note that no sulci are seen over the convexities as they have been effaced due to the Inc. pressure. This situation requires emergency neurosurgery and ventricular shunting to reduce pressure
Aqueductal Stenosis (Non-communicating Hydrocephalus)
Note the prominent enlargement of the lateral and third ventricles in the setting of a normal sized fourth ventricle. Pattern is one of non-communicating hydrocephalus, which occurs from impaired Drainage through the cerebral aqueduct which connects the third and fourth ventricles. Differs from communicating hydrocephalus wherein all the ventricles are enlarged. Note also that the sulci are relatively effaced which excludes the possibility that the enlarged ventricles are simple due to cerebral atrophy (hydrocephalus ex vacuo). In this case, hydrocephalus likely resulted from scarring in the cerebral aqueduct as a consequence of her meningitis as a child
Colloid Cyst of the Third Ventricle and Non-communicating Hydrocephalus
Cyst located in the anterior third ventricle which is obstructing both foramina of Monro, causing hydrocephalus of the lateral ventricles. On the FLAIR image, the transependymal edema can be seen clapping the anterior and posterior horns of the lateral ventricles.
The lesion is a colloid cyst, which is a benign congenital cyst that arises in the anterior third ventricle. They’re often asymptomatic. However, if the cyst enlarges, compressing the foramina of Monro, non-communicating hydrocephalus may develop. Classically this results first in intermittent severe headaches due to intermittent obstruction of the foramina of Monro. Rare cases result in sudden death
Prematurity (non-communicating hydrocephalus)
Note the massive enlargement of the lateral and third ventricles. This pattern is one of non-communicating hydrocephalus, which occurs from impaired drainage through the cerebral aqueduct which connects the third and fourth ventricles. This picture differed from communicating hydrocephalus wherein all the ventricles are enlarged. Note that the cortical ribbon is extremely thin near the skull, from the constant pressure of underlying obstructive hydrocephalus. Before the bony sutures of the skull have fused in a child, hydrocephalus may present as progressive and abnormal enlargement of the head (macrocephaly). In this case, the clause of the hydrocephalus was likely the Intraventricular hemorrhage associated with premature birth, with subsequent scarring and glimpses of the cerebral aqueduct.
Acute Hydrocephalus from Subarachnoid Hemorrhage
Note the subarachnoid hemorrhage in the basal cisterns and fourth ventricle. Also note the prominent hydrocephalus with dilation of the anterior and temporal horns of the lateral ventricles. Acute hydrocephalus is a potential complication of Subarachnoid hemorrhage, either as a consequence of impaired CSF absorption or obstruction of flow within the ventricular system. This situation requires emergency neurosurgery and ventricular shunting
