idiopathic intracranial hypertension (iih) a review of imaging manifestations and interventional...
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Idiopathic Intracranial Hypertension (IIH)
A review of imaging manifestations and interventional treatment
J. Agraval1, B McGuinness1, S Brew1, A Hope1, M Moriarty1, 1Auckland City Hospital, Auckland, New Zealand
Definition
Raised intracranial pressure in the absence of an identifiable aetiology
Theories of aeitology 1,2
1. CSF homeostasis: Inadequate CSF resorption or increased production
2. Venogenica. Venous sinus thrombus
b. Extrinsic venous compression
c. Vasculitis
3. Venous outflow obstruction i.e. Venous sinus stenosis
Controversial regarding whether this is a causal factor or an effect
Cause or effect?Increased
intracranial pressure Intracranial
hypertension
Compression of the collapsible
transverse sinus
Venous outflow obstruction
Venous hypertension
Decreases CSF reabsorption
EpidemiologyThought to be rare (1 case per 100,000 5 ) but increasingly diagnosed due rising prevalence of obesity
Female predominance 8:1 5
“Classic patient”= Overweight woman of reproductive ageIncidence in 20-44y/o overweight women
19 per 100,000 5
Increased estrogen and leptin is also present in overweight patients with IIH
Obesity = substantial risk factor. Theories 1,3,
Increased BMI Increased intrathoracic and intrabadominal pressure elevated central venous pressure
Prothrombotic state in obesity
Increased leptin and estrogen levels in patients with IIH
IIH in Men – epidemiology 6
Older age group often >40 years
Symptom profilesLess likely to report headache
More common to report visual disturbance
Worse visual outcomes: acuity and visual fields
Increased risk of severe visual loss
No differences in BMI Smaller case series describe men less likely to be overweight but BMI not reported
Diagnosis 4
Symptoms and signs related to raised intracranial pressure
CSF opening pressure >25cmH20
Normal CSF composition
No evidence for underlying structural cause MRI with MR venography ideal
Typical Presentation 1
Headaches most common >90%Pressure-like unrelenting
Associated retro-orbital pain
Visual loss – most commonly transient Tunnel vision
Related to transient ischemia of the optic nerve from the increased CSF pressure in optic nerve sheath
Papilledema – often seen in routine or symptomatic visual testing
Typical Imaging findings
- Empty sella: downward herniation of an arachnocele through the diaphragma sella
- Posterior scleral flattening with enlarged and tortuous optic nerve sheaths
- Distal transverse venous sinus stenoses
MR venography
Should be routine in suspected cases to evaluate for either thrombus or stenosis1,12
• Stenosis can be seen in up to 90% of IIH patients12
TOF or PC MRV is usually inadequate and contrast enhanced MRV should be performed
It is the authors personal experience that where contrast MRV is not available, 3D gradient post contrast T1 reformatted in sagittal and coronal planes often enables accurate diagnosis of venous stenoses
CT venography is also a suitable test
Typical Imaging Findings23 year old female with headache, intermittent pulsatile tinnitus and visual disturbance
CSF distension of optic nerve sheaths with posterior scleral indentation on axial T2. Marked concavity to the superior surface of the pituitary on coronal T2 and sagittal T1. Fluid distension of the oculomotor cisterns has also been suggested as a sign of IIH (red arrows).
Venous Stenoses
37 year old male with IIH and typical distal transverse sinus stenoses on contrast MRV 18 year old female with IIH and in
addition to typical distal transverse sinus stenoses has a stenosis of the distal superior sagittal sinus which is a less common but recognised site of stenosis in this condition
Other Presentations 1,4
Pulsatile tinnitis Unilateral “whooshing sound”
Exacerbated by positional change
Relieved by jugular compression
Diplopia due to cranial nerve VI palsy
Skull base CSF leaks – sphenoid via lateral sphenoid cephalocele or mastoid via tegmun typani erosion
Lateral sphenoid cephalocele and Spontaneous Skull Base CSF leaks
Lateral sphenoid cephaloceles and other skull base CSF leaks have clinical manifestations and similar imaging findings to IIH 9,10,11
Retrospective review11 shows high recurrence rate of leak post surgical repair in “spontaneous” cephaloceles and leaks, this is improved if the IIH is also managed
Arachnoid pits (arachnoid granulations outside the dural venous sinuses) are commonly seen in these cases
Lateral sphenoid cephalocele
Multiple arachnoid pits within the middle cranial fossae (yellow arrows), small surgically proven cephalocele into lateral recess of sphenoid sinus (red arrow) with mild edema or gliosis in the adjacent temporal lobe (green arrow)
Distal transverse sinus stenoses and empty sella appearance suggest background IIH
61 year old female presents with recurrent bacterial meningitis and left nasal CSF leak
Other Skull Base Leaks and Meningoceles
58 year old male with longstanding headaches & bilateral mastoid CSF leaks. Surgically repaired with subsequent diagnosis of IIH requiring ventricular shunt
T2 coronalBilateral tegmen dehiscence, mastoid effusions and adjacent left temporal lobe edema
63 year old female with headaches. Other sequences showed empty sella and bilateral transverse sinuse stenoses.
Bilateral CSF enlargement of Meckel’s cave particularly on the left
Natural history
Historically thought of as a “benign” condition hence previous name “Benign intracranial hypertension” 1
Severe visual deficits can occur in 25% without treatment 7
Lower quality of life scores, greater incidence of depression and anxiety 8
Goals of management
Cessation of symptoms, in particular restoration of visual acuity and resolution of papilledema
Treatment (1,3,4): conservative
Weight loss
Carbonic anhydrase inhibitors decrease the rate of CSF production
Acetozolamide
Topiromate (partial antagonist)
Simple analgesics to relieve headache symptoms
Therapeutic lumbar puncture: effects often short lived
Treatment: surgical/endovascular
Reserved for patients with ongoing visual loss despite conservative management OR those with rapid symptom onset
3 Options:CSF shunting – ventriculoperitoneal or lumboperitoneal
Optic nerve sheath fenestration (ONSF)
Venous sinus stenting
Dural venous sinus stenting 3,4
Retrograde transvenous manometry is performed with patient awake as general anaesthesia can give false negative results
threshold for treatment if a gradient >8mm-10mmHg
Only one side needs stenting – usually dominant side
Premedication with dual antiplatelet medication required. The authors continue this for 3 months following stenting then switch to aspirin alone.
Stenting - Technical Issues
Stent trackability – carotid stents are typically used and navigation around the distal sigmoid and jugular bulb is often challenging. A long sheath is essential may need to be tracked intracranially to get stent into position
Post stenting manometry may show transference of stenosis to another site
Trigeminal nerve periorbital referred pain post-stenting is common and may last 2-3 days
Stent During Deployment
Sheath has been advanced to distal sigmoid sinus to enable the stent to track into position
Guidewire tip is in distal superior sagittal sinus with “J” tip to prevent engagement of cortical veins
Stenting Efficacy and Outcome
No prospective or randomized controlled trials
Retrospective cases series (largest 52 patients) suggest stenting is effective in improving symptoms and preserving vision3,4
Serious complications are uncommon but include intracranial (usually subdural) hemorrhage
Re-stenosis adjacent to the stent requiring further stenting occurs in approximately 10%3
Concerns exist about longterm stent patency although delayed in-stent stenosis has not been described.
Case: Adjacent Sinus Stenosis57 year old male with severe IIH presenting
as headache and diplopia due to bilateral VI nerve palsies
Cerebral angiogram shows severe stenosis of the distal superior sagittal sinus and dominant distal right transverse sinus. Right image shows tip and 3cm marker of microcatheter used to perform manometry (red arrows)
Case: Adjacent sinus stenosis
Initial pressure gradient was across the transverse sinus stenosis but after 1st stent was deployed (red arrows) repeat manometry showed transference of pressure gradient to the superior sagittal sinus stenosis and a 2nd stent was deployed (green arrows) with restoration of normal calibre at both sites
57 year old male with severe IIH presenting as headache and diplopia due to bilateral VI nerve palsies
Case: Adjacent sinus stenosis
57 year old male with severe IIH presenting as headache and diplopia due to bilateral VI nerve palsies
Represents 6 months later with recurrence of symptoms and papilloedema. Manometry showed new severe stenosis of mid superior sagittal sinus which was then stented. At 2 years of follow up he remains symptom free with normal vision and no papilloedema
Optic Coherence Tomography (OCT) 14,15
Can be used as an objective assessment of retinal thickness and papilledema to assess response to treatment
Analogous to ultrasound but uses light instead of sound to yield cross sectional images
Provides images on the micron scale Can image the retinal nerve fiber layer (RNFL)
Measure swelling at the optic
Functions as a type of “optic biopsy”
OCT Pre and Post Stenting
Pre-stenting
Post-stenting
Retinal fibre layer thickness (solid line = right eye, dotted line = left eye) is well above the normal range prior to stenting. Near normalization is seen following stenting (right image – small part of left eye is above normal range)
Summary
Posterior scleral indentation, empty sella and distal transverse venous sinus stenoses are typical imaging features of IIH
IIH patients can also present with skull base CSF leaks
Venous stenoses can also occur in the distal superior sagittal sinus
Stenting of the dural venous sinuses is an alternative to shunting for those patients that fail medical treatment
Recurrent stenosis adjacent to stented segments may occur requiring additional stent deployment.
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