Questions:
34. What are the symptoms and signs of idiopathic intracranial hypertension (IIH)?
35. What are the diagnostic criteria for IIH?
36. What is the ideal imaging test when evaluating a patient with presumed papilledema?
37. A patient with bilateral disc swelling has a normal brain MRI. What test should be done next?
38. What should one consider if the headaches of IIH do not improve (at least transiently) after a lumbar puncture?
39. What does a normal Brain MRI in the setting of papilledema suggest?
40. What should be evaluated next in a patient with bilateral swollen discs, normal BP, normal CT with and without contrast, LP opening pressure >250mm and normal or abnormal CSF contents?
41. What should be evaluated next in a patient with bilateral swollen discs, normal BP, normal MRI with and without contrast, LP opening pressure >250mm and normal or abnormal CSF contents?
42. What items are most commonly associated with IIH?
43. What condition can mimic the symptoms of cerebral venous thrombosis?
44. What can early recognition of cerebral venous thrombosis prevent?
45. Should papilledema from a meningeal process or cerebral venous thrombosis be classified as IIH?
46. What are the goals of IIH management?
47. What are the main factors that drive the management of IIH?
48. What MRI findings are supportive of the diagnosis of IIH?
49. When the predominant symptom of a patient with IIH is severe headaches, which surgical procedure is preferred?
50. How often does a lumboperitoneal or ventriculoperitoneal shunt need to be repaired?
51. When the predominant symptom of a patient with IIH is vision loss and headaches are no more than mild, which surgical procedure is preferred?
52. Does optic nerve sheath fenestration usually need to be performed on both optic nerves?
53. How often does optic nerve sheath fenestration fail?
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Questions with answers:
34. What are the symptoms and signs of idiopathic intracranial hypertension (IIH)?
Patients with IIH have symptoms and signs of raised intracranial pressure, such as headaches, nausea, pulsatile tinnitus, papilledema (and visual field loss), and diplopia from unilateral or bilateral sixth nerve palsy.
35. What are the diagnostic criteria for IIH?
1. Signs and symptoms of raised intracranial pressure
2. No localizing neurologic signs, in an alert patient, other than abducens nerve paresis
3. Normal neuroimaging MRI and MRV or CTV studies except for small ventricles, empty sella or other signs of increased ICP
4. Documented increased opening pressure (≥ 250 mm of water) but normal CSF composition
5. Primary structural or systemic causes of elevated intracranial pressure excluded (e.g., chronic meningitis or cerebral venous thrombosis)
36. What is the ideal imaging test when evaluating a patient with presumed papilledema?
MRI of the brain with contrast. It is more sensitive than CT for detecting intracranial masses, infiltrative and meningeal processes, and cerebral venous thrombosis.
37. A patient with bilateral disc swelling has a normal brain MRI. What test should be done next?
A lumbar puncture with measurement of the cerebrospinal fluid opening pressure and CSF analysis should always be performed.
38. What should one consider if the headaches of IIH do not improve (at least transiently) after a lumbar puncture?
That the headaches are unlikely to be entirely the result of raised intracranial pressure. Additional causes for the headaches should be considered.
39. What does a normal Brain MRI in the setting of papilledema suggest?
A meningeal process, venous hypertension, or IIH as the cause of raised intracranial pressure.
40. What should be evaluated next in a patient with bilateral swollen discs, normal BP, normal CT with and without contrast, LP opening pressure >250mm and normal or abnormal CSF contents?
Rule-out venous sinus thrombosis with brain CTV or MRI and MRV.
41. What should be evaluated next in a patient with bilateral swollen discs, normal BP, normal MRI with and without contrast, LP opening pressure >250mm and normal or abnormal CSF contents?
Rule-out venous sinus thrombosis with brain MRV.
42. What items are most commonly associated with IIH?
IIH is most commonly seen in young obese women. The main items associated with IIH are obesity or recent weight gain, sleep apnea syndrome, chronic anemia, medications (vitamin A, isotretinoin, tetracycline, and cyclosporine)
43. What condition can mimic the symptoms of cerebral venous thrombosis?
IIH
44. What can early recognition of cerebral venous thrombosis prevent?
A devastating stroke and visual loss from chronic papilledema.
45. Should papilledema from a meningeal process or cerebral venous thrombosis be classified as IIH?
No, by definition IIH is increased intracranial pressure with normal imaging and normal CSF contents.
46. What are the goals of IIH management?
To relieve headaches, diplopia, and to preserve visual function.
47. What are the main factors that drive the management of IIH?
The severity of headaches and the presence of visual loss, specifically visual field deficits.
48. What MRI findings are supportive of the diagnosis of IIH?
1. enlarged optic nerve sheaths
2. optic nerve tortuosity
3. protrusion of the optic nerve head into the globes
4. concavity or flattening of the posterior globes
5. a reduction in the diameter of the cavernous sinuses
6. a narrowing of Meckel’s (the trigeminal) cave, which normally appears as CSF signal lateral to the posterior cavernous sinus and clivus on axial sections. This is an especially sensitive MRI marker of IIH.
49. When the predominant symptom of a patient with IIH is severe headaches, which surgical procedure is preferred?
Lumboperitoneal shunt or ventriculoperitoneal shunt
50. How often does a lumboperitoneal or ventriculoperitoneal shunt need to be repaired?
In 50% of cases, a lumboperitoneal shunt or ventriculoperitoneal shunt will need to be repaired.
51. When the predominant symptom of a patient with IIH is vision loss and headaches are no more than mild, which surgical procedure is preferred?Optic nerve sheath fenestration
52. Does optic nerve sheath fenestration usually need to be performed on both optic nerves?
Yes, it is usually done first on the side with the eye having worse visual function.
53. How often does optic nerve sheath fenestration fail?
In one-third of cases, optic nerve sheath fenestration fails within 3 years.
The information below is from Neuro-ophthalmology Illustrated-2nd Edition. Biousse V and Newman NJ. 2012. Thieme
9.6 IIH
IIH (IIH), previously called pseudotumor cerebri, is defined as increased intracranial pressure with normal imaging and normal CSF contents. By definition, papilledema from a meningeal process or cerebral venous thrombosis should not be classified as IIH. Patients with IIH have symptoms and signs of raised intracranial pressure, such as headaches, nausea, pulsatile tinnitus, papilledema (and visual loss), and diplopia from unilateral or bilateral sixth nerve palsy. The Management of the disease is based on the severity of headaches and the presence of visual loss, specifically visual field deficits.
9.6.1 Diagnosis of IIH
The criteria for the diagnosis of IIH are as follows:
● Signs and symptoms of raised intracranial pressure (including papilledema)
● No localizing neurologic signs, in an alert patient, other than abducens nerve paresis
● Normal neuroimaging studies (neuroimaging should include a good quality MRI scan ± magnetic resonance venography [MRV] or computed tomographic venography[CTV] to rule out cerebral venous thrombosis). Nonspecific signs of increased intracranial pressure are common and include empty sella, flattening of the globes, dilation of the optic nerve sheath, meningoceles, and stenosis of the intracranial transverse venous sinuses.
● Documented increased opening pressure (≥250mm of water) but normal CSF composition
● Primary structural or systemic causes of elevated intracranial pressure excluded (e.g., chronic meningitis or cerebral venous thrombosis)
9.6.2 Cause of IIH
The cause of this disorder is unknown. It involves most often young, obese women and may be associated with other factors. The main factors associated with IIH are obesity or recent weight gain, sleep apnea syndrome, chronic anemia, and medications (vitamin A, isotretinoin, tetracycline, and cyclosporine).
9.6.3 Treatment of IIH
The goals of the management of IIH are to relieve headaches and diplopia and to preserve visual function (▶Fig. 9.24). There is a high spontaneous remission rate.
The lumbar puncture performed as part of the workup is usually the first step of the treatment, as it immediately decreases the intracranial pressure (at least transiently). Headaches that do not improve (at least transiently) after lumbar puncture are unlikely to be entirely the result of raised intracranial pressure. In rare cases, patients develop rapidly progressive visual loss that requires emergent surgical treatment. A brief course of intravenous steroids is sometimes helpful in this setting, but steroids should not be prescribed routinely or chronically in IIH (because of weight gain and rebound effect)
Surgical treatments in IIH include the following:
● CSF shunting procedures (performed by neurosurgeons) (▶Fig. 9.25)
○ CSF drainage into the peritoneum most often
○ Lumboperitoneal shunt or ventriculoperitoneal shunt
○ Preferred when headaches are severe
○ Obstruction or disconnection requires a revision in about 50% of lumboperitoneal shunts.
● Optic nerve sheath fenestration (performed by ophthalmologists) (▶Fig. 9.26)
○ Decompression of the optic nerve by making a window into its dural sheath from a transconjunctival medial or lateral approach
○ Done on the eye with the worst visual function first (often needs second eye surgery)
○ Preferred when visual loss is predominant and headaches are mild
○ The fenestration fails in up to one third of cases within 3 years.
● Endovascular venous stenting of a stenosed transverse sinus (performed by interventional neuroradiologists) (▶Fig. 9.27)
○ Most IIH patients have bilateral stenoses of the distal portion of the intracranial transverse venous sinus (▶Fig. 9.27). Although these stenoses contribute to the intracranial hypertension
(▶Fig. 9.28), they are not necessarily the primary cause of increased intracranial pressure and they do not need to be treated in most patients.
○ Rarely, endovascular stenting of a stenosed sinus can be proposed to decrease the intracranial venous hypertension and reduce the intracranial pressure.”1
MRI Findings in IIH
Radiology update in neuro-ophthalmology. John H. Pula, Jennifer Daily and Jeffrey DeSanto. Curr Opin Ophthalmol 2011:22:451–457
MRI in IIH requires that brain imaging does not show another cause of increased intracranial pressure. The commonly found ‘slit-like ventricles’ and empty sella are not actually helpful in diagnosing IIH.
Figure 5 Demonstrates items 1, 2, 3 and 4.
Features supportive of the diagnosis including: 1. an enlarged optic nerve sheath, 2. optic nerve tortuosity, 3. protrusion of the optic nerve head, and 4. concavity or flattening of the posterior globes, 5. a narrowing of Meckel’s cave and 6. a reduction in the diameter of the cavernous sinuses.”2
Narrowing of Meckel’s Cave and cavernous sinus and enlargement of the optic nerve sheath in pseudotumor cerebri. Degnan AJ, Levy LM. Journal of Computer Assisted Tomography. 2011:35:2:308-312
Narrowing of the Meckel’s caves in particular is a robust indicator of PTC with a strong sensitivity and specificity.
FIGURE 1. Measurement of the Meckel’s caves in a patient with PTC. Depicted here is the standard measurement used for determining the maximal diameter of the Meckel’s caves on axial T2-weighted images taken of a 36-year-old woman who presented with headache, found to have an opening CSF pressure of 32 cm H2O. The Meckel’s caves measure 0.36 and 0.31 cm, considered narrow in our study. Also noted on imaging were empty sella sign and narrowed venous sinuses in addition to quantitatively narrowed cavernous sinuses as well.
FIGURE 2. A, Bilateral narrowing of Meckel’s cave. Bilateral narrowing of the Meckel’s caves and cavernous sinuses are additional signs seen on axial T2-weighted MRI proposed as indicators of elevated intracranial pressure. This 58-year-old woman presented with visual disturbances and was found to have papilledema. B, Normal Meckel’s caves. This age-matched 58-year-old female patient with vasculitis demonstrates normal-sized Meckel’s caves measuring 0.63 cm bilaterally.
References:
1. Neuro-ophthalmology Illustrated-2nd Edition. Biousse V and Newman NJ. 2012. Thieme
2. Narrowing of Meckel’s Cave and cavernous sinus and enlargement of the optic nerve sheath in pseudotumor cerebri. Degnan AJ, Levy LM. Journal of Computer Assisted Tomography. 2011:35:2:308-312
3 . Narrowing of Meckel’s Cave and cavernous sinus and enlargement of the optic nerve sheath in pseudotumor cerebri. Degnan AJ, Levy LM. Journal of Computer Assisted Tomography. 2011:35:2:308-312
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