DWI ABNORMALITIES IN STATUS EPILEPTICUS

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figures 1, 2, 3, 4 and 5 ( T2, T1, DWI, ADC, FLAIR) show cortical swelling with increased signal intensity in left parieto-occipital region( mainly cortical) on T2/ FLAIR, hypointense signal on T1, increased signal on DWI( suggestive of restricted diffusion) with corresponding low signal on ADC.

A 14 year old girl with history of seizures presented with ongoing generalized seizure activity for the last 3 days. MRI showed altered signal in left frontal( not shown here), parietal and occipital regions involving cortex and minimal subcortical white matter with cortical swelling and increased gyral volume of the affected areas. There was restricted diffusion in these areas suggestive of cytotoxic oedema. The area of abnormal signal did not conform to any vascular territory and was hence thought to be due to sustained seizure activity rather than cerebral ischaemia.

DIFFUSION WEIGHTED IMAGING IN STATUS EPILEPTICUS:

Diffusion weighted imaging( DWI) is an MR technique that allows characterization of tissues according to the degree of water mobility.

Its widest application is still in evaluation of cerebral ischemia where restricted water diffusion is seen early after onset of ischemia. Increased signal on DWI reflects the presence of cytotoxic edema.

DWI abnormalities are also reported in prolonged seizure activity.

DWI signal abnormalities are accompanied by abnormal signal on T2/ FLAIR if MRI is done 24 hours after onset of sustained seizure activity.
If however, MRI is done earlier, DWI may show restricted diffusion in the absence of signal changes on T2/ FLAIR ( as in early cerebral ischemia).

The areas of involvement do not correspond to any vascular territory. Morever, the changes are transient and return to normal after the seizure activity ceases.

Changes are seen as increased signal intensity and swelling of the cortical gray matter, subcortical white matter, or hippocampus on periictal T2/ FLAIR and diffusion-weighted images. These findings reflect transient cytotoxic and vasogenic edema induced by seizure, although this has not been proven pathologically. 

To conclude, it is  important to remember that abnormal processes other than cerebral ischemia can also cause acute diffusion-weighted imaging changes.

 REFERENCES:
1. Kassem-Moussa H, Provenzale JM, Petrella JR et al:Early Diffusion Weighted MR Imaging Abnormalities in Suatained Seizure Activity. AJR 174(5):1304-6, 2000
2.Kim JA, Chung JI, Yoon PH: Transient MR signal changes with Generalized Tonicoclonic Seizures or Status Epilepticus: Periictal Diffusion-weighted Imaging. AJNR 22:1149-60, 2001

CVJ CARIES

Fig 1-STIR coronal

Fig 2 -T2 sag

Fig 3- T1 sag

Fig 4- T2 axial

Fig 5- CT ( axial plane)

A 56 year old man presented with 3 months history of increasing cervical pain and stiffness. MR and CT showed bony destruction involving atlas, axis and occipital condyles with large pre/ paravertebral and epidural collections causing significant thecal sac effacement. The cord was indented but showed no signal change.

Intracapsular Osteoid Osteoma

T1 coronal

T2 coronal

STIR-coronal

T1FS( contrast)-coronal

PDFS-axial

T1FS(contrast)-axial

STIR-coronal

A 27 year old female patient presented with long standing severe left hip pain. Contrast enhanced MRI showed cortical thickening and a small round well-defined area of signal alteration in anteromedial cortex of neck of left femur (isointense signal to skeletal muscle on T1, target apearance on T2/ STIR/PDFS) and  intense peripheral enhancement after contrast suggestive of osteoid osteoma. There is mild effusion in left hip joint.


A non-contrast MR scan performed 6 monthes earlier ( not shown here) showed significant left hip joint effusion and synovial thickening along with a poorly marginated large area of marrow oedema in the left femoral neck. A diagnosis of infective arthritis was made ( the intracapsular osteoid osteoma was overlooked). The patient was treated with antibiotics but showed persistence of pain with mild improvement.

INTRODUCTION: 
 Osteoid osteomas are benign bone forming tumours.

DEMOGRAPHICS:

• 10-25 years of age
• M>F( 3:1)
• Relatively common being 4-10%of primary bone tumours( excluding myeloma)

CLINICAL PRESENTATION:

• Severe pain which is worse at night and is relieved by salicylates or nonsteroidal anti-inflammatory drugs in 80% patients. It is intially intermittent and becomes unremitting later.
• Intracapsular lesions present with signs of synovitis, joint pain and reduced range of movement
• Premature osteoarthritis can occur with chronic intracapsular lesions ( in 50% cases)
• Intracapsular lesions can also cause growth abnormalities
• Muscle atrophy and neurologic signs are rare

IMAGING:
LOCATION:

• Cortical diaphyseal: commonest (65-70%) with femur being the commonest site
• Intramedullary : Rare and involves carpal and tarsal bones
• Intracapsular: usually in femoral neck, calcar. Has also been reported in elbow, foot, wrist, knee and facet joints
• Subperiosteal: Usually intracapsular( common in hip and talus)
• Spine:10% and involves posterior elements( Lumbar commonest site)
• Multifocal synchronous lesions: rare

X-RAY FINDINGS


Cortical diaphyseal:

• Oval lytic lesion with surrounding cortical sclerosis which may obscure lytic nidus
• The nidus may have central calcification which is seen as a raiopaque point called the Bell

Intracapsular( intra-articular):

• Oval lytic lesion in cortex with or without surrounding sclerosis.
• Sclerotic bone may be at distant site from the lesion
• Joint effusion

CT FINDINGS:

• Accurate in specifying location: cortical vs subperiosteal/ intramedullary
• Scerotic reaction seen
• Lytic nidus better seen
• Assciated pathologic fracture may be seen
• Helpful for guidance of percutaneous RF ablation

MR FINDINGS:
Nidus:

• Low to intermediate signal on T1
• Variable intensity on T2 depending on mineralization.
• Intense and dynamic enhancement( maximum in arterial phase)
• With increased spatial resolution, a partially mineralized nidus has a target appearance with mineralized portion appearing hypointense and non-mineralized portion appearing peripherally hyperintense.Nidus may be missed however in cortical bone.

Reactive response:

• Cortical thickening and sclerosis shows low SI on all sequences
• Reactive marrow oedema is seen in 63% cases( low signal on T1, high signal on fluid sensitive sequences)
• Periosteal elevation and adjacent soft tissue reactive changes are seen in 50% cases( high signal on fluid sensitive sequences)
• Effusion is seen in intracapsular lesions

Advantages of MR: It shows not only the nidus and surrounding sclerosis, but also the marrow oedema and articular changes.

NUCLEAR MEDICINE FINDINGS:

• Technetium Bone scan shows very intense round activity at nidus and is highly sensitive
• Double density sign: Very intense central activity at nidus surrounded by less intensity of reactive bone
• Round focus helps differentiate from stress fracture which has more linear activity.

DIFFERENTIAL DIAGNOSIS :

• Arthritis:( As in the index patient)
• Osteosarcoma/ Ewing's sarcoma
• Stress fracture
• Chronic osteomyelitis

TREATMENT:

• CT Guied radiofrequency ablation is treatment of choice
• Surgical resection

REFERENCES:

• Manaster BJ: Osteoid Osteoma: Diagnostic Imaging:Musculoskeletal non-traumatic disease. Amirsys.2-26, 2010
• Chai JW et al: Radiologic Diagnosis of Osteoid Osteoma: From Simple to Challenging Findings.  Radiographics; 30(3): 737:49,2010
• emdicine. medscape. com

INTRAOCULAR CYSTICERCOSIS

T2WI of right orbit showing an intraocular cystic lesion abutting the optic nerve head

T1 W sequence showing a hypointense lesion in the posterior part of the globe

FLAIR image showing subretinal cyst with suggestion of a hyperintense scolex posteriorly

FLAIR axial image showing Co-existent cysticercosis in the brain

FLAIR axial image showing co-existent cysticercosis lesions in brain

A 22 year old young man presented with epilepsy and blurring of vision in right eye. An MRI of his brain showed neurocysticercosis with an intra-ocular cystic lesion in right globe in keeping with ocular cysticercosis.

INTRODUCTION: Cysticercosis is a parasitic infection caused by the larval form of pig tapeworm, T solium. The humans act as an intermediate host in the life cycle of the worm and contracts the disease following ingestion of eggs in contaminated water or food. After ingestion, the eggs form primary larvae which disseminate to different parts of the body( central nervous system and skeletal muscles). Once intracranial, the primary larvae develop into secondary larvae, cysticerci..
Ocular disease is reported to occur in a significant number of patients with cysticercosis.

CLINICAL PRESENTATION:
-Blurring/ loss of vision
-Distorsion of images
-Sensation of light flashes
-Periorbital pain
-Diplopia
-Ptosis

DISCUSSION:
The human eye is vulnerable to many infectious diseases. It is important to identify and timely treat these diseases to prevent loss of vision.

Most parasitic infections of the eye arise from blood borne carriage of the micro-organisms to the eye.
The extra-ocular muscles form the most common type of orbital cysticercosis.
In the ocular form, vitreous and subretinal space are the preferential sites. Anterior chamber presentation is very rare.

Diagnosis is usually by direct ophthamoscopic demonstration.
Ultrasound, CT and MRI are imaging modalities described in establishing the diagnosis.
MRI is the best imaging tool for intraocular as well as neurocysticercosis.
If not clearly identified on routine MR sequences, high resolution CISS sequence has been found to be helpful in identifying the ocular lesions.

REFERNCES:
-Nijjar IBS, Singh JP, Arora V, Abrol RA, Sandhu PS, Chopra R, Roopa. MRI in intraocular cysticercosis- A Case Report. IJRI 2005; 15:3

RIGHT ACOUSTIC NEUROMA CAUSING TRIGEMINAL NEURALGIA

Axial T1C+ MR scan showing enhancing right acoustic schwannoma with ice cream on cone appearance

 Coronal T1C+ MR showing the enhancing right acoustic schwannoma

Sagittal CISS image showing compression of the right trigeminal nerve by the acoustic schwannoma

Sagittal CISS image showing normal left trigeminal nerve for comparison.

A 54 year old lady presented with right sided deafness, vertigo and right trigeminal neuralgia.
MRI revealed a right acoustic neuroma compressing the right trigeminal nerve.