Etiology and Diagnosis of
Intracranial Hypertension:
Using MRI to Narrow an
Index Patient’s Differential
Michael A. Dyer
Harvard Medical School, July 2009
Beth Israel Deaconess Medical Center
Department of Radiology
Dr. Gillian Lieberman
Objectives
Using an index case of a patient with
intracranial hypertension (IH), this
presentation will provide the skills and
knowledge necessary to:
„
Recognize the signs of IH on MRI
„
Understand the logical basis for the differential
diagnosis of IH
„
Develop a foundation for systematically approaching
MR scans in patients with IH
Our Index Patient:
Chief Complaint, History, and Physical
„
34 year-old woman with chronic headache (recently worsened) and
blurred vision referred to an ophthalmologist
„
Complicated medical history,
including 50 lb weight gain in the
past 1-2 years
„
Physical exam: optic disc swelling,
i.e. papilledema (see figure)
„
Referred by the ophthalmologist
for an MRI to look for the potential
cause of the patient’s signs and
symptoms
Papilledema
(Bienfang, DC; UpToDate)
Before looking at our patient’s MRI, we’ll
review
(1) a few points about CTs and MRIs; and
(2) a few points about different MRI
sequences
Menu of Tests: CT vs. MRI
in Patients with Papilledema
„
„
Depending on the suspected cause of a patient’s
papilledema, physicians may choose to order a CT and/or an
MRI
„
For example, as we will explore later in the presentation,
subarachnoid hemorrhage is one potential cause of
papilledema; in a patient with acute subarachnoid hemorrhage,
CT is usually the test of choice
„
MRI, on the other hand, is preferable to CT for diagnosis of
many other causes of papilledema, e.g. soft tissue lesions
This presentation concentrates only on diagnosis using MRI
Distinguishing
MRI Sequences
„
“T1” = T1 weighted image (fluid is dark, i.e. low intensity)
„
“T2” = T2 weighted image (fluid is bright, i.e. high intensity)
„
“C+” = Image enhanced with gadolinium (i.e. IV contrast was
administered)
„
“FLAIR” = Fluid attenuated inversion recovery (a sequence that
nulls signals from fluids to allow visualization of
lesions whose signals are normally obscured by the
signal from cerebrospinal fluid)
„
“MP-RAGE” = Magnetization prepared rapid acquisition gradient
echo; designed for rapid image acquisition (a T1
weighted scan)
Now let’s look at our patient’s MRI
Our Patient: Evidence of
Intracranial Hypertension on MRI
Our Patient
Normal
Findings
„
Increased fluid in
optic nerve
sheath bilaterally
(bright signal)
„
Mild flattening of
posterior globes
„
Tortuous optic
nerves
Axial T2 MRI
Axial T2 MRI
(PACS BIDMC)
(PACS BIDMC)
What fluid could be responsible for the high
intensity signal surrounding the optic nerve
within the optic sheath?
Review of CSF Flow
„
CSF can track along potential space surrounding optic nerve
CSF Production and Flow
(Cummings, B; IUPUCAnatomy)
CSF in Optic Nerve Sheath
(Corkrey O'Hara, JK website)
CSF and
Intracranial Hypertension
„
Increased pressure within the intracranial
compartment is necessary for CSF to track along
the optic sheath
„
Sometimes intracranial hypertension causes other
findings, such as hydrocephalus
Now let’s review some basic principles of
intracranial pressure to understand what
could underlie our patient’s MRI findings that
are suggestive of intracranial hypertension
Compliance and
Intracranial Pressure
„
Compliance is equal to change in volume divided
by change in pressure (C = ΔV / ΔP)
→ The cranial compartment is incompressible
(i.e. it has a low compliance)
→ If compliance is low, then for a given
increase in volume, there will be a large
increase in pressure (ΔP = ΔV / C)
„
Therefore, any change in volume of the structures
or fluids within the cranium will produce large
changes in pressure
As a result, to generate a differential
diagnosis for intracranial hypertension (and
therefore, to find a cause for the patient’s
papilledema and orbital MRI findings), let’s
consider what inside the intracranial
compartment could be increased in volume
Major Physical Components
of the Intracranial Compartment
1. Blood
2. Brain
3. CSF
Causes of Intracranial
Hypertension: Differential Diagnosis
1. Increased blood volume
2. Increased brain volume
3. Increased CSF volume
Causes of Intracranial
Hypertension: Differential Diagnosis
1. Increased blood volume
a. occlusion (e.g. venous thrombosis)
b. blood outside vessels (i.e. hemorrhagic stroke)
2. Increased brain volume
3. Increased CSF volume
Causes of Intracranial
Hypertension: Differential Diagnosis
1. Increased blood volume
a. occlusion (e.g. venous thrombosis)
b. blood outside vessels (i.e. hemorrhagic stroke)
2. Increased brain volume
a. intracranial mass (e.g. tumor)
b. cerebral edema
3. Increased CSF volume
Causes of Intracranial
Hypertension: Differential Diagnosis
1. Increased blood volume
a. occlusion (e.g. venous thrombosis)
b. blood outside vessels (i.e. hemorrhagic stroke)
2. Increased brain volume
a. intracranial mass (e.g. tumor)
b. cerebral edema
3. Increased CSF volume
a. increased production (e.g. from choroid plexus papilloma)
b. decreased absorption/obstruction to CSF outflow
Let’s look at our patient’s MRI more closely
to consider each of these potential causes
of our patient’s IH
We will also look at MRIs from other
patients (whom we will call “companion
patients”) for comparison
Companion Patient 1: Venous
Thrombosis on MRI (Differential 1a)
Venous Thrombosis
Index Patient: Normal
(filling defect in superior
and straight sagittal sinuses)
Sagittal C+ T1 MRI
(Poon, CS, et al; AJROnline)
Sagittal C+ T1 MRI
(PACS BIDMC)
Companion Patient 2: Subarachnoid
Hemorrhage on MRI (Differential 1b)
Subarachnoid Hemorrhage
Index Patient: Normal
(high intensity signals in basal cisterns)
Axial FLAIR MRI
(Medscape)
Axial FLAIR MRI
(PACS BIDMC)
Companion Patient 3: Metastatic
Tumor on MRI (Differential 2a)
Tumor
(heterogeneously enhancing lesion in the
lateral ventricle: a metastasis from the lungs)
Axial C+ T2 MRI
(PACS BIDMC)
Index Patient: Normal
Axial C+ T1 MRI
(PACS BIDMC)
Companion Patient 4: Cerebral
Edema on MRI (Differential 2b)
Cerebral Edema
Index Patient: Normal
(enhancing fluid suggestive
of vasogenic edema)
Axial C+ FLAIR MRI
(PACS BIDMC)
Axial FLAIR MRI
(PACS BIDMC)
Companion Patient 5: Choroid Plexus
Papilloma on MRI (Differential 3a)
Choroid Plexus Papilloma
(heterogeneous lesion in the lateral ventricle)
(hydrocephalus from increased CSF production)
Axial T2 MRI
(RadsWiki)
Index Patient: Normal
Axial T2 MRI
(PACS BIDMC)
Companion Patient 6: Obstructive
Hydrocephalus on MRI (Differential 3b)
Obstructive Hydrocephalus
(large vestibluar schwannoma)
(hydrocepahalus due to obstruction)
Sagittal MP-RAGE MRI
(PACS BIDMC)
Index Patient: Normal
Sagittal MP-RAGE MRI
(PACS BIDMC)
Having examined MRIs of our patient
juxtaposed with MRIs of relevant
companion patients, we now return to our
differential
In our Patient’s MRIs,
Did We See Any Evidence for the
Following Diagnoses in Our Differential?
1. Increased blood volume
a. occlusion (e.g. venous thrombosis)
b. blood outside vessels (i.e hemorrhagic stroke)
2. Increased brain volume
a. intracranial mass (e.g. tumor)
b. cerebral edema
3. Increased CSF volume
a. increased production (e.g. from choroid plexus papilloma)
b. decreased absorption/obstruction to CSF outflow
We Saw No Evidence
of Increased Blood Volume
1. Increased blood volume
a. occlusion (e.g. venous thrombosis)
b. blood outside vessels
2. Increased brain volume
a. intracranial mass (e.g. tumor)
b. cerebral edema
3. Increased CSF volume
a. increased production (e.g. from choroid plexus papilloma)
b. decreased absorption/obstruction to CSF outflow
We Saw No Evidence
of Increased Brain Volume
1. Increased blood volume
a. occlusion (e.g. venous thrombosis)
b. blood outside vessels
2. Increased brain volume
a. intracranial mass (e.g. tumor)
b. cerebral edema
3. Increased CSF volume
a. increased production (e.g. from choroid plexus papilloma)
b. decreased absorption/obstruction to CSF outflow
And We Saw No Evidence
of Increased CSF Volume
1. Increased blood volume
a. occlusion (e.g. venous thrombosis)
b. blood outside vessels
2. Increased brain volume
a. intracranial mass (e.g. tumor)
b. cerebral edema
3. Increased CSF volume
a. increased production (e.g. from choroid plexus papilloma)
b. decreased absorption/obstruction to CSF outflow
We created a differential diagnosis for our patient by logically working
through the components of intracranial pressure and intracranialcompartment volume
Yet we saw no evidence in our patient of any of the diagnoses on the
differential
Therefore, we have no etiologic explanation for the patient’s
intracranial hypertension
What do we call diseases for which we
have no etiologic explanation?
Causes of Intracranial
Hypertension: A More Complete
Differential Diagnosis
1. Increased blood volume
a. occlusion (e.g. venous thrombosis)
b. blood outside vessels
2. Increased brain volume
a. intracranial mass (e.g. tumor)
b. cerebral edema
3. Increased CSF volume
a. increased production (e.g. from choroid plexus papilloma)
b. decreased absorption/obstruction to CSF outflow
4. Idiopathic Intracranial Hypertension (i.e. Pseudotumor Cerebri)
Pseudotumor Cerebri:
A Diagnosis of Exclusion
Idiopathic Intracranial Hypertension (IIH) = Pseudotumor Cerebri
(two names for the same diagnosis)
Dandy Criteria:
ƒ
Symptoms and signs of increased intracranial pressure (e.g. headache,
transient visual obscurations, pulse synchronous tinnitus, papilledema, visual
loss)
ƒ
No other neurologic abnormalities or impaired level of consciousness
ƒ
Elevated intracranial pressure with normal cerebrospinal fluid (CSF)
composition
ƒ
A neuroimaging study that shows no etiology for intracranial hypertension
ƒ
No other cause of intracranial hypertension apparent
Pseudotumor Cerebri: Clinical
Presentation and Epidemiology
„
Presentation
„
„
„
„
„
„
„
„
Headache (92% of patients)
Transient visual obscurations (72%)
Intracranial noises (pulsatile tinnitus) (60%)
Photopsia (54%)
Retrobulbar pain (44%)
Diplopia (38%)
Sustained visual loss (26%)
Epidemiology
„
„
Annual incidence: 1-2 per 100,000 people
Higher in obese women ages 15-44 years old: 4-21 per 100,000
Pseudotumor Cerebri:
Presentation on MRI
„
„
„
„
„
„
Flattening of the posterior sclera (80% of patients)
Empty sella (70%)
Distension of perioptic subarachnoid space (50%)
Enhancement (with gadolinium) of the prelaminar
optic nerve (45%)
Vertical tortuosity of the orbital optic nerve (40%)
Intraocular protrusion of the prelaminar optic
nerve (30%)
Our Patient:
Diagnosis and Follow-Up
„
Following MRI, lumbar puncture showed
elevated opening pressure and normal CSF,
confirming suspected diagnosis
„
Treated with diuretics; advised to lose weight
„
Presented at ED a week later with diplopia
and headache
Our Patient: Intracranial
Hypertension on MRI at Follow-Up
ƒ
Presented with same
findings as on previous MRI
ƒ
Treated with lumbarpuncture drainage of CSF
ƒ
Prescribed medication for
headache prophylaxis
ƒ
Treatment will be ongoing
and will be aimed at
alleviation of symptoms and
prevention of permanent
vision loss
Index Patient: Follow-Up
(Can you identify the same 3 findings
identified on our patient’s MRI on slide 8?)
Axial T2 MRI (PACS BIDMC)
Summary
„
Understanding the basic anatomy and physiology of the
intracranial compartment allows for the logical
formulation of a differential diagnosis for intracranial
hypertension
„
Radiologic imaging modalities such as MRI are used not
only to identify patients with characteristic “Aunt Minnie”
findings indicative of a particular disease, but also to
make diagnoses of exclusion, such as pseudotumor
cerebri (i.e. idiopathic intracranial hypertension)
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Acknowledgements
Special thanks to Maria Levantakis for
guidance regarding format, Dustin Lewis for
help with editing and formatting, and Dr.
Adam Jeffers for guidance regarding
content and images