E. Lee Murray, MD
CHAPTER CONTENTS
◦Nonobstructive Hydrocephalus from Increased CSF Production
◦Nonobstructive Hydrocephalus from Reduced CSF Resorption
◦Fourth Ventricular Outflow Lesions
OVERVIEW
Cerebrospinal fluid (CSF) is formed by the choroid plexus and ependyma and absorption is by the arachnoid granulations that protrude into the venous sinuses, as well as by CNS lymphatics. CSF circulation can be disordered by a mismatch in formation and resorption or occlusion of CSF conduits. Some of the potential defects affecting CSF circulation include:
•Increased CSF pressure from increased CSF production, decreased CSF resorption, or, in the case of pseudotumor cerebri, from unknown causes
•Decreased CSF pressure, especially CSF leak
•Occlusion of CSF flow at various levels producing obstructive hydrocephalus
•Normal-pressure hydrocephalus, a specific condition possibly related to impaired absorption
INCREASED CSF PRESSURE
Increased CSF pressure can be from:
•Nonobstructive hydrocephalus from increased CSF production
•Nonobstructive hydrocephalus from reduced CSF resorption
•Increased CSF pressure without hydrocephalus, e.g., pseudotumor cerebri
Pseudotumor cerebri is discussed in detail in Chapter 20. This is differentiated from the other disorders by the absence of increased ventricular size.
Nonobstructive Hydrocephalus from Increased CSF Production
Nonobstructive hydrocephalus from increased CSF production is usually a disorder of children but can occur in adults. A choroid plexus papilloma produces more CSF than is usually resorbed. The lesion is usually benign but can be malignant. Location is most commonly in the lateral ventricle.
PRESENTATION is with symptoms of increased intracranial pressure (ICP), which can include headache, nausea, and vomiting. With markedly increased ICP, patients can become drowsy. Exam often shows papilledema unless the onset is fairly acute. Visual loss can be insidious but detectable on exam. Cranial nerve palsies are most commonly of CN 3 and CN 6.
DIAGNOSIS is suspected when a patient presents with headache and papilledema and there is concern for increased ICP. Brain imaging with computed tomography (CT) or magnetic resonance imaging (MRI) shows increased ventricular size and can visualize choroid plexus lesions.
MANAGEMENT is usually surgical. Some patients need urgent shunting to relieve pressure, followed later by surgical excision of the lesion. Depending on pathology, location, and success of surgery, other treatments including radiation therapy and/or chemotherapy may be considered.
Nonobstructive Hydrocephalus from Reduced CSF Resorption
Nonobstructive hydrocephalus from reduced CSF resorption is usually due to one of the following:
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