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TUTORIAL: Clinical PET - Neurology
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Infantile Spasms
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Infantile spasms are characterized by brief flexion, extension, or mixed flexion-extension jerks of the muscles of the neck, trunk, or extremities. They are an age-specific entity, occurring usually between 3 and 8 months of age. Although the cause of infantile spasms is often determinable (e.g., structural abnormalities), a number of patients display symptoms without an identifiable structural abnormality. Shown above on the left is the MRI from a 13 month-old child with infantile spasms. Note that the MRI appears normal.
The corresponding FDG image on the right, from a PET scan taken during an interictal period, shows an area of hypometabolism in the occipito-temporal cortex (arrowheads). Surface electrode recordings, taken from this cortical region during surgery, confirmed that this tissue was the source of the epileptic spasms.
Surgical Resection
The tissue that was confirmed to be the source of the spasms was surgically resected. The extent of cortical resection in such patients closely corresponds to the region of hypometabolism defined by the pattern of glucose utilization revealed by the preoperative PET scan.
Click on image above to view full-size image.
Post-operatively, the MRI reveals only the loss of tissue. In contrast, the post-operative PET scan shows recovery of function (glucose metabolism) throughout the remaining brain tissue, concomitant with the elimination of spasms. Neuropathological examination of resected cortical tissue revealed microscopic cortical dysplasia. Overall, research suggests that PET with FDG, even when there are normal findings on CT and MRI, is highly sensitive in detecting developmental focal dysplastic lesions of the brain. The use of PET also obviates the need for chronic intracranial electrographic monitoring prior to cortical resection. Instead, at the time of surgery, electrocorticography can be performed to delineate the area of epileptogenicity and determine the extent of cortical resection more precisely.
Credits
Material for this section was kindly provided by:Michael E. Phelps, Ph.D.
Dept. of Molecular and Medical Pharmacology
UCLA School of Medicine
Harry T. Chugani, M.D.
Pediatric PET Center
Children's Hospital
Wayne State University
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