Hair analysis for drugs of abuse by radioimmunoassay and gas chromatography/mass spectrometry (GC/MS) is an effective means for identifying drug abusers. Hair can be collected under close supervision without embarrassment and is not subject to evasive maneuvers (false negatives) such as temporary abstention, excessive fluid intake, and substitution or adulteration of specimens. Hair analysis has a wide window of detection ranging from months to years and provides information concerning the severity and pattern of an individual's drug use. Hair analysis is also not subject to evidential false positives, such as those caused by poppy seed ingestion, spiking of drinks or food, and mix-up or contamination of specimens. In part, these problems can be avoided because hair analysis can always be repeated with a newly collected specimen. The results of animal experiments and of various clinical, forensic, and criminal justice applications are described.

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Twenty-two patients whose electroclinical ictal characteristics suggested frontal lobe seizure foci were studied. Computed tomography (CT) scans showed abnormalities in only 32% of patients whereas magnetic resonance imaging was informative in 45%. 18FDG-Positron emission tomography (PET) scanning revealed decreased metabolism in 64% of the group. The areas of hypometabolism were focal, regional, or hemispheric. Focal frontal hypometabolism was significantly correlated with the electroclinical (semiologic) ictal localization. Therefore, FDG-PET scanning is a sensitive and specific technique for investigating patients with seizures of probable frontal lobe origins.

We performed dynamic ['8F]fluorodeoxyglucose (["FJFDG) positron emission tomographic (PET) analyses in 8 patients.Rate constants of influx (K,*), efflux (k2*), phosphorylation (k3*), and dephosphorylation (k4*) were derived for the regions of interest (ROIs), which included (1) the hypometabolic epileptogenic regions and (2) the homologous regions in the contralateral hemispheres. In addition, the four constants were determined from at least one clearly defined (control) ROI from the same plane and its homologous contralateral ROI. Influx (K,*) in the epileptogenic region was reduced in comparison with the contralateral ROI. Reductions in influx (K,*), which averaged 18 f 13% (mean -t SD),["FIFDG phosphorylation (k3*) (25 -t 20%), and brain glucose utilization rates (26 f 10%) were observed in the epileptogenic region. Reductions in efflux were not statistically significant (k2* = 13 f 28%) but were comparable in magnitude to the average reduction in K,*. No ipsilateral versus contralateral differences were seen for any rate constants measured outside the epileptogenic region. Influx correlated highly with phosphorylation in the epileptogenic region. Our data suggest that the hypometabolic epileptogenic focus seen in ["FJFDG-PET studies is also a region of reduced blood-brain barrier glucose transporter activity and that reductions in phosphorylation are proportional to reductions in ["JFDG influx. Cornford EM, Gee MN, Swartz BE, Mandelkern MA, Blahd WH, Landaw EM, Delgado-Escueta AV. Dynamic [ '*F] fluorodeoxyglucose positron emission tomography and hypometabolic zones in seizures: reduced capillary influx. Ann Neurol 1998;43:801-808 From the