Clinical importance of somatosensory evoked potentials in early diagnosis of syringomyelia.

We report a rare case of syringomyelia, the development of which was monitored by somatosensory evoked potentials. The evoked potentials recorded over an eight months' period of time were correlated with the incidence of syringomyelia. Changes of the evoked response latency and amplitude were dtected. The evoked potential change and the sensation deficit indicated a pathological process. High-resolution MRI revealed syringomyelia in the cervical and the thoracic segments of the spinal cord. Somatosensory evoked potentials represent a sensitive diagnostic method recording changes in the biopotentials. Potential changes require localisation of a possible process and high-resolution MRI. Evoked potentials enable to monitor both, the disease development, but also the healing process (Fig. 3, Ref 11).

Somatosensory-evoked potentials and MRI in tuberculous spondylodiscitis.

Early diagnosis of spondylodiscitis is a condition of efficient conservative treatment. Somatosensory-evoked potentials with clinical examination results are used in assessing the diagnosis, as well as in monitoring the course of disease and healing. MRI clearly shows the inflammatory process, healing and scars. We report a 46-year-old woman suffering from non-specific interscapular pains. The evoked somatosensory potentials of the tibial nerveshow potential conductivity being slowed down through the thoracic spine, which is clearly evident from the prolonged latency and the decreased amplitude of the evoked response. The performed thoracic spine MRI shows spondylodiscitis at the Thl0-11 level. The subject is a nurse administering BCG therapy at a urology clinic, due to the fact of which this was deemed to have been a case of tuberculous spondylodiscitis. Due to the possibility of scattering the causative agent by needle, the biopsy was given up and antituberculous therapy was administered ex juvantibus. The disease was followed up by clinical examinations, somatosensory-evoked potentials and MRI up to fully successful and final recovery from spondylodiscitis. The above examinations are of great help in diagnosing the tuberculous spondylodiscitis and monitoring the recovery (Fig. 6, Ref. 16).

Neurophysiological mechanisms underlying motor evoked potentials in anesthetized humans. Part 1. Recovery time of corticospinal tract direct waves elicited by pairs of transcranial electrical stimuli.

Direct (D) corticospinal tract discharges were recorded epidurally in patients at anesthetic depths suppressing indirect (I) activity and were elicited by two equal transcranial electrical stimuli. The recovery of amplitude of the second D wave (D2) was a function of the interstimulus interval (ISI) and the stimulus duration. For example, with a 100 micros pulse, there was no response at an ISI of 1.1 ms, but partial recovery occurred with a 500 micros pulse. This indicates a relative refractory component at this ISI. Both D2 amplitude and conduction time recovered completely using a 4 ms ISI, with evidence of increased amplitude and reduced conduction time (supernormality) at longer ISIs. These findings are relevant in explaining high frequency D and I discharges and facilitation of motor responses by two transcranial magnetic pulses. Furthermore, these data help to understand why an ISI of 4 ms would be optimal in eliciting limb muscle responses when a short train of transcranial stimuli elicits only D waves in anesthetized patients (Deletis et al., Clin Neurophysiol 112 (2001) 445).

Similarities in the pattern of regional brain dysfunction in negative schizophrenia and unipolar depression: a single photon emission-computed tomography and auditory evoked potentials study.

1. Negative schizophrenic and unipolar depressive patients were clinically assessed. In addition to this SANS and HRSD tests were administered. 2. SPECT and AEP measurements were provided. SPECT resulted in quantified brain blood perfusion, by means of average "count/pixel" values in the brain regions of interest. AEPs resulted in stored multichannel signal waveforms. 3. Statistical analyses of blood perfusion measurement data revealed an overall similarity between these two disorders in the majority of brain regions. An exception to this are the regions: inferior temporalis, inferior occipitalis, hippocampus and the anterior basal ganglia. Both diagnostic groups manifested hypofrontality. In general, hypoperfusion of the left hemisphere was found, albeit displaying different patterns in the two groups investigated. 4. AEP latencies were prolonged and found to be similar in both diagnostic groups, whilst AEP amplitudes were smaller in schizophrenics compared to depressives.

[Diagnosis of focal epilepsy using electroencephalographic brain mapping]. / Prilog dijagnostici zarisnih epilepsija s pomocu tehnike cerebralne kartografije elektroencefalograma.

By means of the EEG brain mapping method we analyzed electroencephalograms of patients who presented focal abnormalities in standard EEG. A total of 15 patients with various epileptic manifestations was investigated. According to the etiology of the disease, they were divided into 3 groups: microfactor, stationary macrofactor, and non-stationary macrofactor. The brain mapping technique proved to be very useful as imaging method of focal abnormalities, useful for registering asymmetries in reaction to following of intermittent photostimulation. The method is especially suitable for storing findings and chronological comparison of findings during pharmacological therapy. The specificity of the method regarding the etiological factor and type of epileptic manifestation could not be verified in such a small number of patients.