Oral Exam - CNS Flashcards
Dural tear findings
In111-DTPA cisternogram:
Extravasation of radiotracer into the extradural space
Cribiform plate leak findings
Tc99m -DTPA cisternogram:
Activity extending below the skull base and into the frontal sinus, nose, and nasopharyxn
Activity in stomach suggests rhinorrhea due to swallowing
Activity in bladder or kidney = dose extrav
CSF leak protocol
Intrathecal 0.5 mCi In111 or Tc99 DTPA
○ 2, 6,. 12, 24 hours imaging
- Pledgets - Pack counts positive if > 1.5 x blood
CSF Shunt patency study protocol
Supine
0.5 mCi In/Tc DTPA 25G needle into reservoir
Expect clearance into abdomen within 15-20 minutes
LEAP with Tc99, Medium energy collimator with In111
Serial ant planar q1 min x 20 min
+/- SPECT CT to help localize
Shunt occlusion locations
Children = proximal tubing more common
Adults -= distal
Shunt occlusion finings (distal occlusion)
Activity confined to CSF space
Absent activity in peritoneal cavity
Abrupt termination of activity along expected course of shunt tubing
NPH Protocol
0.5 mCi In111-DTPA intrathecal
Planar images 4, 24, 48 hrs
Radionuclide cisternography - Normal findings
– 1hr: Radiotracer reaches basal cisterns
– 2-6hrs:Radiotracer reaches Sylvian fissures
– 12hrs:Radiotracer reaches cerebral convexities
– 24hrs:Radiotracer reaches superior sagittal sinus and
is absorbed by arachnoid villi
Normally noradiotracer enters ventricles, although transient activity in ventricles at 4 hrs is still considered normal
NPH findings
○ NPH
– Radiotracer activity in ventricles at ≥ 24hrs
– Absence of radiotracer activity in cerebral convexities
by 24 hrs
□ Heart configuration: Appearance of radiotracer
activity in lateral ventricles on anterior view
□ Comma (also c-shaped) configuration: Appearance of radiotracer activity in lateral ventricles on lateral
views
□ Butterfly configuration: Appearance of radiotracer
activity in lateral ventricles on posterior view
○ SPECT/CT can help confirm ventricular activity
NPH symptoms
Gait disturbance, urinary incontinence, dementia
NPH DDx
DDx:
AD - Type II or IIIa flow pattern
Normal aging - Type II pattern
Non-communicating hydrocephalus - normal actiivty in convexities
– Type II: Delayed activity in cerebral convexities at 24
hrs without ventricular activity
□ Cerebral atrophy or aging
– Type IIIa: Radiotracer activity in cerebral convexities at
24 hrs with early transient ventricular activity □ Indeterminate (can be seen with
noncommunicating hydrocephalus, developing or resolving communicating hydrocephalus, or cerebral atrophy)
– TypeIIIb:Noradiotraceractivityincerebralconvexities at 24 hrs with early transient ventricular activity
□ Suggestive of NPH (communicating hydrocephalus)
– TypeIV:Noradiotraceractivityincerebralconvexities at 24 hrs with persistent ventricular activity
□ SuggestiveofNPH(communicatinghydrocephalus)
AD Amyloid PET findings
Amyloid PET best for ruling out AD
F18 florbetapir
○ Absence of amyloid plaque rules out AD in patients with
dementia
– View in black-on-white background at high contrast levels
– Cerebellumgray-whitedifferentiationisbaselinefor
discerning normal gray matter from physiologic tracer
retained in white matter
– Signs of amyloid deposition
□ Decreasing cortical gray-white differentiation compared to cerebellar gray-white differentiation
□ Increasing gray matter uptake int emporal,parietal, and frontal cortices
□ Uptake in posteriorcingulategyrus
AD F18-FDG PET OR HPMPAO/ECD SPECT findings
Posterior temporal and parietal + posterior cingulate
Sparing of sensorimotor, basal ganglia, thalamus, primary visual cortex
Mild cognitive impairment findings
Medial temporal lobe hypometabolism: Most
sensitive marker for predicting MCI
AD FDG protocl
□ Patient should fast, stop IV fluids containing dextrose, stop parenteral feeding for 4-6 hrs
□ Bloodsugarshouldbe<150-200mg/dL
□ Patientshouldbeplacedinquiet,dimlylitroom
prior to and after injection for 30 min
– Radiopharmaceutical:F-18FDG
– Dose:5-20mCi
– Dosimetry:Urinarybladderreceiveslargestdose
– Imageacquisition: 30-60minafterinjection
Frontotemporal - best imaging tools
• Bestimagingtool
○ F-18FDGPEThelpstodifferentiatebetweenFTDand
other causes of dementia, e.g., Alzheimer disease (AD)
and Lewy body disease (DLB)
○ PET/SPECTmaybeusedinearlydiagnosis
○ Correlateswithdiseaseprogression
• SPECT
○ 2nd-linestudyifF-18FDGPETisnot
available/reimbursed