Combining cutaneous silent periods with quantitative sudomotor axon reflex testing in the assessment of diabetic small fiber neuropathy.

OBJECTIVE: Routine electrophysiological testing is often normal in the evaluation of painful diabetic neuropathy, as it is unable to detect dysfunction of thinly myelinated (Aδ) and unmyelinated (C) small fibers. Although cutaneous silent periods (CSP) and quantitative sudomotor axon reflex testing (QSART) respectively evaluate these fiber types in the extremities, these two tests have yet to be assessed together. METHODS: 26 patients with a clinical diagnosis of small fiber neuropathy (SFN) and 26 age-matched controls were assessed. Nine patients had Type I diabetes, nine had Type II diabetes, and eight had impaired glucose tolerance. The CSP onset latency and duration were recorded in each extremity. QSART was performed on the right side. RESULTS: 58% (15/26) of patients had abnormal sweat volumes obtained from QSART, while 50% (13/26) of patients had abnormal CSP responses. Combining these two tests increased the sensitivity of testing to 77% (20/26). Abnormalities were seen equally across all patient groups. CONCLUSIONS: Combining CSP with QSART significantly increases the sensitivity of testing when assessing patients with SFN related to diabetes, or prediabetes. SIGNIFICANCE: For clinically suspected SFN, it is preferable to test more than one small fiber type, as each possess different structural and functional properties and may be heterogeneously affected between patients.

Amygdala volumetry in "imaging-negative" temporal lobe epilepsy.

OBJECTIVE: Although amygdala abnormalities are sometimes suspected in "imaging-negative" patients with video EEG confirmed unilateral focal epilepsy suggestive of temporal lobe epilepsy (TLE), amygdala asymmetry is difficult to assess visually. This study examined a group of "imaging-negative" TLE patients, estimating amygdala volumes, to determine whether cryptic amygdala lesions might be detected. METHODS: Review of video EEG monitoring data yielded 11 patients with EEG lateralised TLE and normal structural imaging. Amygdala volumes were estimated in this group, in 77 patients with pathologically verified hippocampal sclerosis (HS), and in 77 controls. RESULTS: Seven of 11 "imaging-negative" cases had both significant amygdala asymmetry and amygdala enlargement, concordant with seizure lateralisation. Although significant amygdala asymmetry occurred in 35 of 77 HS patients, it was never attributable to an abnormally large ipsilateral amygdala. Compared with patients with HS, patients with amygdala enlargement were less likely to have suffered secondarily generalised seizures (p<0.05), and had an older age of seizure onset (p<0.01). CONCLUSION: Abnormal amygdala enlargement is reported in seven cases of "imaging-negative" TLE. Such abnormalities are not observed in patients with HS. It is postulated that amygdala enlargement may be attributable to a developmental abnormality or low grade tumour. It is suggested that amygdala volumetry is indicated in the investigation and diagnosis of "imaging-negative" TLE.

Degree of hippocampal atrophy is not related to a history of febrile seizures in patients with proved hippocampal sclerosis.

OBJECTIVES: To examine the degree of hippocampal atrophy in patients with temporal lobe epilepsy and proved hippocampal sclerosis to determine whether or not patients with febrile seizures have more severe hippocampal atrophy. To determine whether or not there is a relation between age of seizure onset, duration of temporal lobe epilepsy, or seizure frequency, and severity of hippocampal atrophy. METHODS: Hippocampal volumes were measured from volumetrically acquired MR images in 77 consecutive surgical patients with temporal lobe epilepsy (37 febrile seizures (FS)+, 40 FS-) with proved hippocampal sclerosis, and compared with 98 controls. RESULTS: Ipsilateral and contralateral hippocampal volumes were not significantly different between the FS+ and FS- groups. There was no difference in the age of onset of habitual seizures, duration of epilepsy, or age at the time of surgery, between these groups. No clinically significant correlations were found between hippocampal volumes and age of onset of first non-febrile seizure, duration of temporal lobe epilepsy, or complex partial and secondarily generalised seizure frequency, in patients with and without febrile seizures. CONCLUSIONS: Although febrile seizures was associated with hippocampal sclerosis in 48% of patients in this surgical series, the degree of MRI determined hippocampal atrophy was not related to a history of such seizures. The results do not support the view that febrile seizures cause more severe hippocampal sclerosis and are consistent with the hypothesis that hippocampal sclerosis is a pre-existing abnormality.