Neurological Disorders: Pseudotumor Cerebri

What is it?

Pseudotumor cerebri (PTC), now-a-days also called as idiopathic intracranial hypertension (IIH), is more frequently seen in women, especially the obese ones. This neurological disorder presents with abnormally raised pressure inside the skull cavity and presents with severe headache & problem with vision. A Neurologist is frequently involved in the care of these patients.

Identifying this condition and instituting proper treatment is of paramount importance as patients can lose their vision due to this disease.

Anatomical aspects of this disease

Inside our brain tissue there are cavities called as ventricles and the cerebrospinal fluid (CSF) flows through these ventricles. CSF is secreted inside the ventricles and flows through them and finally exits the ventricular system and reaches the sub-arachnoid space, a CSF containing space formed between the two coverings of brain and spinal cord called as pia and arachnoid membranes. In PTC the CSF pressure is pathologically elevated and precipitates the above mentioned symptoms.

What causes pseudotumor cerebri?

At this moment it is crystal clear that the CSF pressure builds up in side the skull cavity in PTC patients, but with regard to how exactly this abnormal increase in CSF pressure happens is still not clear although there are many theories put forward. Impaired absorption of CSF is a dominant hypothesis although it is difficult to explain then why it doesn’t result in hydrocephalus (enlargement of ventricles). All in all the process development of PTC appears to be very complicated one, at least for the time being.

By convention idiopathic intracranial hypertension diagnosis is made only if it is idiopathic in nature, means no cause is found. If a causative factor is identified then it s called as secondary PTC. Such secondary causes which can produce a similar picture include;

• Medications like tetracycline
• Vitamin A and its derivatives, example - acne products
• CVT (cerebral venous thrombosis)
• Endocrine disorders like hypothyroidism, birth pill usage
• SLE (Lupus) etc.

Obesity is a common accompaniment especially of idiopathic PTC.

How does pseudotumor-cerebri patient manifest?

• Headache of varying severity
• Blurring of vision
• Loss of vision
• Nausea
• Vomiting
• Double vision
• Swelling of optic nerve (nerve of vision inside the eye)

Headache is usually diffuse and varies in intensity. The blurring of vision is serious symptom as it indicates the optic nerve is getting involved due to the CSF pressure effect. If the disease progresses then there is a threat of further damage to this nerve and loss of vision.

Diagnosis

The following investigations are necessary to establish the diagnosis;

• CT or MRI scan of the brain
• CSF analysis

If MRI is available it is preferred over CT as it gives more detailed anatomical picture of the brain. These imaging studies are used to look for any structural pathology to explain the raised ICP (intracranialpressure) as well as any hydrocephalus (enlarged ventricles).

CSF opening pressure is what clinches the diagnosis. Up to about 190 to 200 mm water pressure is ok anything above that is suspicious and above 250 along with typical manifestations is almost diagnostic for PTC.

CSF is also sent for routine, and as needed for any special lab tests.

Treatment

Treatment is conservative & surgical.

Conservative management includes;

• Stopping the offending agents
• Weight loss (strongly recommended)
• Diamox (acetazolamide)
• Lasix (frusemide, less commonly used compared to Diamox)
• Rarely steroids like prednisolone
• Headache medications

The surgical options are mainly two types;

• CSF shunt placement
• Optic nerve sheath fenestration (ONSF)

The CSF shunt can be placed into the lateral ventricles (ventriculoperitoneal shunt) or to the lumbar thecal sac (theco peritoneal shunt).

ONSF is performed when there is a threat to losing the vision due to optic nerve damage. This procedure will not help with the Pseudotumor Cerebri headache though, for which shunt placement may be necessary if conservative therapy fails.

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