Imaging Abnormalities with MRI

Question 1

What are T1 images?

Answer 1

Short TR and short TE
Images – CSF fluid looks dark
Blood and fat are bright
Brain pathology, low signal
Used usually after initial screening T2 MRI to further investigate area of concern

Question 2

What are T2 images?

Answer 2

Long TR and long TE
CSF appears bright
Brain pathology, high signal
Solid masses, cysts and sub-acute blood is bright
Acute bleeds, chronic bleeds and fat are dark
Usually used with initial screen of MRI

Question 3

What are diffusion weighted imaging MRI?

Answer 3

Measures the rate of water diffusion in the brain (cellular changes)
Infections and cerebral abscess
Acute ischemic stroke
Sensitive in early detection of infarct within minutes of symptoms
Differentiates tumors from other lesions
Solid mass vs cyst looks different (cyst is fluid/pus filled)

Question 4

What is proton density MRI?

Answer 4

Type of MR image where there is a mixture of T1 and T2 techniques
Long TR and short TE
Hyper-intensifies white matter against lower signal CSF
Still available but largely replaced by FLAIR for brain imaging
Used in some neurological disorders for visualizing specific tissue characteristics and quantifying disease progress

Question 5

What is proton density with flair MRI?

Answer 5

Fluid Attenuated Inversion Recovery
Image contrast for detecting abnormalities; pathology more visible
T2 weighted image with CSF suppression
Detects lesions in and around the ventricles
Multiple Sclerosis plaques
Helpful in stroke, tumor, abscess or hemorrhage

Question 6

Are CT and MRI complimentary in the diagnosis and treatment of skull-base lesions?

Answer 6

Yes

Question 7

What are some skull-base symptoms?

Answer 7

Headaches
Vision disturbance
Facial weakness
Dizziness
Pain or discharge
Hearing loss
Tinnitus

Question 8

When are contrast agents with MRI used?

Answer 8

Primarily in pathologies that disrupt the brain, labyrinth, or nerves, as well as inflammatory conditions, or vascular abnormalities
Tumors or masses in the brain (CPA tumors, schwannoma, meningioma, epidermoid, cholesterol granuloma (CHL, bluish color of TM), paraganglioma (red mass behind TM), and endolymphatic sac tumor)

Question 9

What is a cholesterol granuloma?

Answer 9

Benign cysts consisting of granulation tissue prone to bleeding; expanding mass
Characteristic blue TM due to granular tissue behind the ear drum
50% have history of ear trauma or surgery
Can occur with recurrent ear infections
Fat can be bright or dark depending on T1 or T2, flips
Location: middle ear, petrous apex, or mastoid
Surgery: depends on location and symptoms
MRI: hyperintense on both T1 and T2, and should not change with gadolinium enhancement

Question 10

What does hemotympanum look like?

Answer 10

Blood behind the TM
Gives it a purple hue

Question 11

What is a glomus tympanicum?

Answer 11

Benign but invasive
Pulsatile tinnitus
Hearing loss
Red mass (vascular) behind intact TM - does not extend to hypotympanum
CT- well defined soft tissue mass overlying cochlear promontory
MRI- salt & pepper appearance

Question 12

What are endolymphatic sac tumors?

Answer 12

CT and MRI complimentary
Rare locally invasive tumor of the endolymphatic sac
Aggressive tumor associated with von Hippel-Lindau disease
Vestibulocochlear symptoms are not an indication of a tumor (~60% with symptoms do not have tumors, 30% are bilateral). Presents with hearing loss (95%), tinnitus (92%), vertigo or disequilibrium (62%), aural fullness (29%)

Question 13

What are common lesions in the CPA?

Answer 13

Vestibular schwannoma
Meningioma (usually does not widen the IAC; grows length wise along the nerve)

Question 14

What do you use to visualize CPA tumors?

Answer 14

Contrast enhanced MRI
CT widening of the IAC, erosion of the bone

Question 15

What are the presenting symptoms for CPA tumors?

Answer 15

Hearing loss - 95%
Tinnitus - 80%
Vertigo/unsteadiness - 50-75%
Headache - 25%
Facial hypesthesia - 35-50%
Diplopia - 10%

Question 16

What are vestibular schwannomas?

Answer 16

Account for 6-10% of all intracranial tumors
Benign, 40-60 years, 95% sporadic, 5% NF
Hearing loss, tinnitus, and vestibular complaints
1% of SSNHL, imaging finds the VS
10% of VS will have SSNHL, treatment is the same, steroids
Arise in the mid to lateral portion of the IAC (Scarpa’s ganglion) and sometimes the CP angle - IAC is approximately 1cm, growth rate of all IAC tumors combined ~ 0.5-2.0mm/year
MRI with gadolinium

Question 17

What is intracanalicular vestibular schwannoma?

Answer 17

Contained entirely within the IAC
35% will grow slowly over 10 years
Wait and see approach
Regular MR Imaging (every 6 months)
Less frequent MRI after 5 years of monitoring (several years)

Question 18

What is extracanalicular vestibular schwannomas?

Answer 18

Outside the IAC
Up to 70% have a high growth rate
More aggressive management, especially large tumors
May require resection

Question 19

What are meningiomas?

Answer 19

Located anywhere the meninges are found
Meninges (protective covering of the brain)
Tumors are external to the brain tissue
Low rate of recurrence
Mass is isointense to gray matter on both T1 and T2 weighted imaging
Symptoms include headache, paresis and change in mental state
Symptoms change depending on the location of the tumor and mass effect on surrounding structures

Question 20

What are the 3 layers of meninges?

Answer 20

Dura mater
Arachnoid mater
Pia mater

Question 21

What are the three spaces between the meninges?

Answer 21

Epidural space
Subdural space
Subarachnoid space

Question 22

What medical conditions involve the meninges?

Answer 22

Meningitis
Hematoma
Meningioma

Question 23

What are CPA meningiomas?

Answer 23

Most common type of brain tumor
Grows on the surface of the brain or spinal cord
Meningiomas can present in the IAC or posterior cranial fossa
Presentation: Dizziness/vertigo and hearing impairment
T1 with contrast - contrast will define the outline of the mass

Question 24

Are epidural hematomas and extradural hemorrhage the same thing?

Answer 24

Yes

Question 25

What is epidural hematoma?

Answer 25

Associated with head trauma or skull fracture Most commonly a tear in the middle meningeal artery Collection of blood between the inner surface of the skull and outer layer of the dura Mass effect May or may not lose consciousness with ongoing headache CT and MRI can both be used in diagnosis Shaped like a lemon

Question 26

What is subdural hematoma?

Answer 26

Trauma/head injury (15%) or Atraumatic (3-5%) - venous tearing of subcortical veins Collection of blood between the dura and the arachnoid mater Can happen at any age Due to falls in elderly May not have a clear history of trauma Mass effect Severe persistent headache Level of consciousness decreases gradually CT and MRI can both be used in diagnosis Shaped like a banana

Question 27

What is meningitis?

Answer 27

Infection of the meninges membranes that cover your brain and spinal cord Symptoms include neck pain and sudden high fever, hearing loss, balance disorder, tinnitus Bacterial meningitis - hearing should be tested ASAP Viral meningitis – less severe symptoms than bacterial Meningeal enhancement is Non-specific Differential Dx: neoplasm, hemorrhage, inflammatory disorders

Question 28

What are arachnoid cysts?

Answer 28

CT or MRI for diagnosis Can be congenital or occur after injury Fluid filled tumors originating on one of the 3 layers surrounding the brain and spinal cord Can be posterior fossa or middle cranial fossa Symptoms include headache, seizures, vision problems, hearing loss, dizziness, etc. depending on the location of the cyst

Question 29

What are arnold chiari malformation?

Answer 29

Condition in which brain tissue extends through the foramen magnum Cerebellar tonsils are squeezed down possibly affecting the CSF flow of 4th ventricle Symptoms include: headache, dizziness, tinnitus, occipital pain with coughing/sneezing, vision issues, weakness/numbness in limbs, slurred speech, and trouble swallowing MRI is the diagnostic test for choice with CSF flow study

Question 30

What is multiple sclerosis?

Answer 30

MRI contrast helps identify MS pathology T1 weighted images, fat is bright and cerebrospinal fluid (CSF) is dark T2 weighting, fat is dark and CSF is bright Proton density (PD)/FLAIR weighting produces further image contrast - identifies inflammatory demyelinating lesions at different stages in their evolution Typical locations for MS lesions: juxtacortical/cortical, periventricular, and white matter of the brainstem, cerebellum and spinal cord Periventricular lesions are frequently located along the callosal-septal interface and perpendicularly oriented to the long axis of the corpus callosum (radiate like sunshine)