Somatosensory Evoked Potentials Testing Research Articles

Long-term follow-up of total penile reconstruction with sensate osteocutaneous free fibula flap in 18 biological male patients.

Surgical reconstruction of the penis is challenging because of the many cosmetic and functional (e.g., sexual intercourse and voiding) requirements that must be addressed. Since the free sensate osteocutaneous fibula flap was first described for total penile reconstruction in 1993 it has been widely accepted, with its advantages and minimal shortcomings. In this article, the authors present the longest follow-up of biologically male patients with free fibular phalloplasties. Since 1994, 18 biologically male patients with total penile losses for various reasons were treated with free sensate osteocutaneous fibula flaps. All patients were included in the study. The ages of the patients ranged between 20 and 26 years (mean, 22.2 years). The average follow-up period was 5.4 years (range, 1 to 9 years). Patient satisfaction was evaluated by a questionnaire regarding both quality of orgasm and daily activities. Conventional radiographic imaging, magnetic resonance imaging, and bone mineral densitometry were performed to evaluate the fate of the bony component of the flap. Also, sensibility was evaluated by bulbocavernous reflex and penile somatosensory evoked potentials testing in nine patients. Six patients married, and five of them had six children. Most patients and their partners reported pleasurable sexual intercourse and orgasm. Conventional radiographs of the fibular bone in neophalluses showed robust, calcified bone structure without any evidence of bone resorption or fracture. The magnetic resonance images showed the cortical substance and spongiosum of the bone marrow, which are characteristic signs of bone viability. After intravenous injection of gadolinium, the neophallus bone showed uptake of contrast medium. Viability of neophallus bone was shown even at 9-year follow-up (the longest follow-up in the literature). Dual energy x-ray absorptiometry measurements of the penile bone grafts showed that fibular components in the penis had bone mineral density values that were close to but lower than those of intact fibula in the same subjects. These results were considered as evidence of viability of bone grafts. Neural integrity was found between the nerves of the neophallus and the residual penile bodies by both bulbocavernous reflex and penile somatosensory evoked potentials tests. In conclusion, free sensate fibula flap phalloplasty provides the cosmetic and functional requirements that an ideal penis should have. All results put an end to the discussion that the fibular component of the neophallus could resorb. Constitution of neural integrity is important in terms of pleasurable sexual intercourse. The authors believe the free sensate osteocutaneous fibula flap should be considered as the standard in penile reconstruction.

Finger movement is associated with attenuated cutaneous reflexes recorded from human first dorsal interosseous muscle.

Cutaneomuscular reflexes (CMR) have been recorded from the first dorsal interosseous muscle (1DI) of the preferred hand, somatosensory evoked potentials (SEP) were recorded from the contralateral sensory cortex and the sensory nerve action potential (SNAP) was recorded from the median nerve of 15 adult subjects whilst electrically stimulating the digital nerves of the index finger. Subjects performed the following tasks (a) a sustained abduction of the index finger against resistance at 10-20 % maximum voluntary contraction (MVC), and (b) abduction of the index finger as in (a) whilst performing self paced low amplitude tapping of the (i) index finger, (ii) thumb, (iii) middle finger, (iv) little finger and (v) ipsilateral foot. The E2 component of the CMR and the N20/P25 components of the SEP were significantly reduced during finger tapping (P < 0.05). This reduction was independent of which finger was tapping (P > 0.05). There was a significant (qualitative) relationship between the decrease in the size of the E2 component of the CMR and the N20/P25 components of the SEP ((2) test; P < 0.05). There were no significant changes in E1 and I1 (P > 0.05). The size of the SNAP was independent of task (P > 0.05). The size of the E1, I1, E2 components of the CMR, and the N20/P25 components of the SEP were unaltered during foot tapping (P > 0.05, n = 4). We conclude that the decrease in size of the E2 component associated with finger tapping results from gating of the digital nerve input.

Physiologic studies of male sexual dysfunction in multiple sclerosis.

We conducted this investigation to better define the neural disruptions that result in sexual dysfunction in men with multiple sclerosis (MS), using genital electrodiagnostic testing and nocturnal penile tumescence and rigidity monitoring. Thirteen men with MS and sexual dysfunction were recruited for the study. Twelve healthy, sexually potent men were enrolled as controls. All underwent pudendal somatosensory evoked potential (SEP) testing using standard methods, and a new modification to isolate the right and left dorsal nerves of the penis. RigiScan testing was performed on the MS subjects to assess nocturnal erectile function. Unilateral and bilateral DNP SEPs were able to be performed on the control subjects. In all but one MS subjects, DNP SEP abnormalities were found. Three men had normal latency bilateral DNP SEP latencies, but on unilateral DNP testing, abnormalities were identified. Seven men, including those with abnormal or absent SEP latencies, had normal nocturnal erectile activity. There was no correlation between overall functional status, presence of abnormal or absent SEP, and quality of nocturnal erectile activity. Genital SEP abnormalties are common in men with MS and sexual dysfunction. Unilateral DNP SEP testing was more sensitive in identifying abnormalities than the standard method of pudendal SEP testing. One of the causes of sexual dysfunction in men with MS may be due to genital somatosensory pathway disruption, with sparing of the efferent tracts in some men.

Ischial pressure sores treated with a sensate gracilis myocutaneous flap

There are problems in finding a definitive treatment of ischial pressure sores because recurrence is frequently observed. The aim of surgical procedures is to cover the ischial region with stable and durable tissue, which has a good neurovascular supply. If the patient with ischial pressure sores has sensation above L3 level, the sensate gracilis musculocutaneous flap can be used to treat the defect after resection of the decubitis. This treatment was performed in 12 paraplegic patients in whom sensation was absent below the L3 level. The median age of the patients was 32.5 years, with ten males and two females. Four patients had recurrent pressure sores. The average time of follow-up was 8 months. Sensation was assessed with moving finger tip pressure, warm and cold cylinders, two point discrimination and dermal cortical somatosensory-evoked potential tests. Sensation was present in the transferred flap. Although the gracilis myocutaneous flap can also be used as a nonsensory flap for the reconstruction of ischial pressure sores in paraplegic patients under L3 level, the sensate gracilis myocutaneous flap should be chosen primarily when there is sensation over the gracilis region.

Nutritional status in non-alcoholic sub-clinical porto-systemic encephalopathy.

AIM:To understand the role of nutritional status in cirrhotic patients without clinical porto-systemic encephalopathy (PSE).METHODS:Fifty-one non-alcoholic patients with cirrhosis without PSE were studied prospectively and compared with 20 healthy volunteers. The nutritional evaluation included serum prealbumin, albumin, transferrin, body mass index (BMI), mid-arm muscle circumference (MAMC), and grip power. The occurrence of subclinical PSE (SPSE) was defined when N20-N65 inter-peak latencies of median nerve-stimulated somatosensory evoked potentials were > 2.5 standard deviations of control means. Blood chemistries were tested within 12h of somatosensory evoked potentials test and nutritional evaluation.RESULTS:Twenty-five, 17 and 9 cirrhotic patients were graded as Child-Pugh class A, B, and C, respectively. Twenty-four (47.1%) patients developed SPSE. Cirrhotic patients with SPSE had lower serum albumin (2.8g/dL ± 0.5g/dL vs 3.1g/dL ± 0.7g/dL, P < 0.001) levels than those without SPSE. Prealbumin (10.6mg/dL ± 5.7mg/dL vs 12.5mg/dL ± 5.8mg/dL), transferrin (164mg/dL ± 46mg/dL vs 178mg/dL ± 58mg/dL), BMI (23.7kg/m(2) ± 2.7kg/m(2) vs 25.3kg/m(2) ± 3.6kg/m(2)), MAMC (22.2cm ± 2.6cm vs 22.7cm ± 3.5cm), and grip power (26.3kg ± 6.4kg vs 26.9kg ± 6.8kg) were not different between cirrhotic patients with and without SPSE. N20-N65 inter-peak latencies were correlated with serum albumin levels (P =0.01) but not with prealbumin, transferrin, BMI, MAMC,or grip power. Serum albumin, prealbumin and transferrin levels were different among cirrhotic patients with Child-Pugh classes A, B, and C (P < 0.05). BMI, MAMC, and grip power were not different among Child-Pugh classes A, B and C.CONCLUSION:Our data suggest that serum albumin level is a simple test in the evaluation of nutritional status in patients with cirrhosis.

Somatosensory evoked potentials of the posterior tibial nerve in hemiparetic patients: Relation to stance balance and walking ability

Objectives: To examine the association between stance ability and walking performance of poststroke hemiplegic patients and their posterior tibial nerve somatosensory evoked potentials (SEPs). Design and Setting: Fifteen patients, residents of a geriatric rehabilitation hospital, were evaluated twice, with a 2-week interval between sessions. In each session, clinical tests of stance balance and walking ability were performed, and bilateral SEPs to stimulation of the posterior tibial nerve were recorded. Eight healthy, age-matched control subjects underwent the same tests in a single session, but SEPs were recorded unilaterally. Correlation analysis and analysis of variance (ANOVA) were used for studying the prognostic value of the initial posterior tibial nerve SEP measurements as well as the within- and between-sessions relationships between the clinical-functional tests and the SEP data. Results: No significant correlations between the initial SEP values and functional improvement were established. Within each session, positive significant correlations existed between decreased latencies of several of the medium-latency SEP waves and the performance of stance and gait tasks. However, the between-sessions improvement in stance balance was not correlated with a decrease in latency of the SEP peaks or with an increase in their amplitudes. As to walking ability, in those patients whose gait significantly improved, a significant shortening of P37 and P54 latencies took place. Conclusions: The association between the initial and/or the 2-week changes in SEP of the posterior tibial nerve and improvement in stance and walking abilities is equivocal. In addition, the applicability of SEP measurements is limited by patients' physical status and cooperation. The clinical significance of posterior tibial nerve SEP testing in poststroke hemiparetic patients is therefore debatable.

Motor cortical reflex myoclonus: a case study with MEG

Cortical reflex myoclonus usually depends for its generation on the hyperexcitability of sensory cortex, which manifests itself as an enhanced somatosensory evoked potential (SEP). A 25-year-old female, presenting with involuntary jerky dorsiflexion of the left foot, was found to have cortical reflex myoclonus which was aggravated during intended movements. The jerks were also elicited by electrical stimulation of the posterior tibial nerve, although the SEP evoked by the same stimulus was normal in latency and amplitude. Both the spontaneous spikes and the premyoclonus spike demonstrated by jerk-locked back averaging were localized to the superior frontal gyrus, just anterior to the paracentral sulcus. Paired-pulse magnetic stimulation disclosed lack of inhibition in the right hemisphere leg motor area, whereas the excitability of sensory cortex as studied by paired SEP testing was normal. This suggests that the myoclonus was caused mainly by enhanced excitability of the motor cortex and that this alone was enough for the production of long loop reflexes. We propose to designate this type of cortical myoclonus as motor cortical reflex myoclonus. It is generated in the motor cortex, but is at the same time stimulus-sensitive.

Median Nerve Somatosensory Evoked Potentials in Cervical Syringomyelia

Median nerve somatosensory evoked potentials (SEPs) were recorded in 30 patients with cervical syringomyelia before and after surgery. The different SEP components were compared with clinical somatosensory findings. The N13 potential (generated in the dorsal horn at C5-C6) was pathological in 85% of the upper extremities, or 90% of the patients, and correlated with pain/temperature as well as vibration/joint position sense; it was of higher sensitivity in syringomyelia than any other clinical symptom or SEP component. P14 (brain stem) and N20 (postcentral cortex) were less often affected and correlated with only vibration/joint position sense. Short-term postoperative clinical or SEP changes were most often seen after syringoendoscopy and less often after syringostomy, resection of cerebellar tonsils, or tumor extirpation. Alterations of SEPs after surgery occurred in more patients (60%) than did changes in clinical condition (approximately 27%); there was, however, no general correlation between these findings. We conclude that median nerve SEP testing with a proper recording technique identifying the different subcortical components is a valuable supplement in the pre- and postoperative diagnostic evaluation of syringomyelia and is of higher sensitivity than clinical somatosensory examination alone.

SEP testing in deeply comatose and brain dead patients: the role of nasopharyngeal, scalp and earlobe derivations in recording the P14 potential

Median nerve somatosensory evoked potentials (SEPs) were tested in 50 patients (20 brain dead, 18 comatose and in 12 progessing from coma to brain death, i.e., 32 cases with brain death and 30 cases with coma were recorded). Derivations were taken from nasopharynx, earlobes, scalp, and neck using cephalic and non-cephalic references. Cortical and subcortical SEP components were evaluated, focussing on the P14 potential. There is evidence that rostral and caudal parts of the P14 generator (lemniscus medialis) are differently affected in brain death, resulting in an abolition of the rostral part, while occassionally leaving intact for some time the caudal part. Non-cephalic referenced scalp records pick up the whole P14 dipole, whereas nasopharyngeal and earlobe derivations pick up different parts of P14, depending on the reference used. Scalp-to-nasopharynx records derive the most rostral part of P14; this “rostral P14” was bilaterally lost in all brain dead patients, but preserved in all deeply comatose patients with diffuse brain-sttem injuries. Scalp-to-earlobe records in contrast, picked up a P14 dipole segment reaching more caudally, resulting in a P14 potential also in brain dead patients. It is concluded that midfrontal scalp-to-nasopharynx derivations give the moset valuable contribution to the electrophysiological assessment of brain death versus deep coma.

Drug-induced Hypotension SEP Test and Acetazolamide Test Using &lt;SUP&gt;133&lt;/SUP&gt;Xe SPELT in Patients with Occlusive Carotid Disease

The correlation between the drug-induced hypotension somatosensory evoked potential (SEP) test and regional cerebral blood flow changes after acetazolamide administration was studied. Fourteen patients presenting with transient ischemic attack, reversible ischemic neurological deficits, or minor completed stroke were evaluated. All patients had no or only localized low-density areas on computed tomographic scans, and unilateral occlusion or severe stenosis of the internal carotid or middle cerebral artery on cerebral angiograms. The Diamox asymmetry enhancement (DAE) was studied to detect reduced cerebral perfusion reserve in the affected hemispheres. The DAE was 7.9 +/- 5.8% in seven patients positive in the SEP test, significantly higher than -1.5 +/- 2.9% in patients negative in the SEP test. Postoperative SEP tests were negative in all five patients who underwent extracranial-intracranial (EC-IC) bypass surgery, suggesting that the EC-IC bypass improved the cerebral perfusion reserve in the affected hemispheres. The DAE decreased significantly in four of these patients. This study disclosed a significant correlation between the drug-induced hypotension SEP test and DAE. These parameters are considered important for evaluating patients with hemodynamic compromise and/or suitable candidates for EC-IC bypass.

The diagnostic significance of long-latency reflexes in multiple sclerosis

Reflexes of thenar muscles after median or radial superficial nerve stimulation have been investigated in both hands of 47 patients with probable or definite multiple sclerosis (MS) and compared with somatosensory evoked potentials (SEPs) to median nerve stimulation. A delay or absence of long-latency reflexes (LLRs) was found as pathological patterns. The results after median or radial superficial nerve stimulation were usually both pathologic or both normal except in cases with latencies at the upper limit of normal values. Pathological results of reflex testing were obtained in 61% of the patients with probable MS and in 79% of those with definite MS. Abnormal SEPs were found in 44% of the patients with probable MS compared to 62% with definite MS. All cases which had pathologic SEPs also had pathologic LLR. Hence, LLR testing detected more abnormalities than the routine median nerve SEP testing that has been used.

Comparison of the Yield of Somatosensory Evoked Potential Test and Magnetic Resonance Imaging in Myelopathies

Jabbari, Bahman; Urban, Eward; Chu, Anita; Bartoszek, David; Schlatter, Margaret Author Information

Extracranial-intracranial Bypass for Intracranial Main Trunk Artery Stenosis

Extracranial-intracranial (EC/IC) bypass as surgical treatment for ischemic cerebrovascular diseases has been performed since 1973. The reliability of the authors' mehtods of selecting candidates for EC/IC bypass were evaluated through long-term follow-up of 14 patients (mean age, 54 years) who underwent bypass surgery for 50% to 95% stenosis in the intracranial portion of the internal carotid artery (ICA) and/or the middle cerebral artery (M1 or M2) . The interval from the last stroke to bypass surgery ranged from 22 hours to 6 months (mean, 42 days). Computed tomography, cerebral angiography, cerebral blood flow (CBF), and somatosensory evoked potentials (SEP) were evaluated preoperatively. Seven patients were considered candidates for EC/IC bypass because they had decreased hemispheric or regional CBF. In 3 of these 7, improvement or worsening were shown by electroencephalography (EEG) and measurement of SEP during druginduced hypertension or hypotension (drug-induced EEG and SEP test: DEE test). In the other 7 patients bypass surgery was felt to be indicated on the basis of the angiographic findings and the preoperative clinical course. The bypass was patent in 12 patients and not patent in 2. The term of follow-up averaged 4.4 years. One patient experienced a transient ischemic attack in the ICA on the affected side, and another suffered an additional reversible ischemic neurological deficit (RIND) in the vertebrobasilar (VB) system; the latter patient died of a stroke in the VB system 1.5 years after the RIND. Nine of the 14 patients were leading an independent, useful life at the last follow-up visit, and 5 had died, 1 of a stroke and 1 of purulent meningitis. In 3 cases the cause of death was unknown. EC/IC bypass appears somewhat effective in preventing cerebral ischemia, although the mortality rate in this study was rather high (42%). Considering the results of the Cooperative EC/ IC Bypass Study, selecting candidates on the basis of clinical symptoms and angiographic evidence of steno-occlusion of the main trunk of the carotid system is not satisfactory. The patients most likely to benefit from EC/IC bypass will be those in whom the procedure improves CBF and cerebral metabolism. Measurement of CBF and cerebral metabolism, as well as DEE testing, are indispensable in determining whether or not EC/IC bypass is indicated.

Evoked Potential Testing: Clinical Applications

Evoked potential tests have assumed an increasing importance in the practice of a number of specialties, but mostly in neurology. The surprisingly rapid growth in popularity of these procedures seems to have outstripped the care and circumspection that should be exercised when accepting a relatively new diagnostic test into the investigative armamentarium. Obviously, one major reason for their popularity is that they are noninvasive, totally harmless, painless (except for the somatosensory evoked potential test, which may be uncomfortable), and can be carried out by a technician who requires little additional training beyond what has already been learned as an electroencephalographic technician. Perhaps these are all reasons why these tests have become overused and, unfortunately, often misinterpreted. This book, regrettably, does little to address this important problem. It is an excellent manual for the technically inclined and should be indispensable to the physician or scientist setting up a laboratory for the

Brachial plexus injuries. Prognosis of postganglionic lesions.

One hundred ninety-eight cases of postganglionic brachial plexus injury with no signs of combined damage to preganglionic sites were treated conservatively. Among them, 50 whole, 32 upper and 13 lower type injuries were followed up for at least 2 years and the course of the progression of the individual muscle was observed. In the whole type, 44% showed good functional recovery, although some of them needed reconstructive surgery. Thirty-eight percent recovered usefully only in the muscles innervated by upper roots. Three out of 50 cases did not recover at all. There were no particular differences between the whole and upper types with regard to the recovery rate of the arm muscles. However, the upper type showed better functional recovery than the whole type. If the muscles innervated by upper roots could gain a strength of M1 before 9 months after injury, and muscles innervated by lower roots reached M1 before 12 months, their final results were more than M3. But muscles with a strength of less than M2 at 18 months did not recover to more than M3. The muscular power at 24 months was almost the same as the final results. About half of the postganglionic brachial plexus injuries which did not combine preganglionic lesions showed favorable spontaneous recovery with conservative treatment. At the exploration of the brachial plexus, if the somatosensory evoked potential test is positive, which negates the possibility of root avulsion, and also if there is no definite discontinuity of the postganglionic nerves, it should be treated conservatively.(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation of functional reversibility of ischemic brain --to select appropriate patients with completed stroke for STA-MCA bypass surgery.

The purpose of this paper is to present a new method by which the functional reversibility of the ischemic brain can be evaluated by changes of somatosensory evoked potentials (SEP) in induced-hypertension. The method (called functional SEP test) was useful in selecting appropriate candidates of completed stroke for superficial temporal artery (STA)—middle cerebral artery (MCA) anastomosis. To evaluate the grade of reversible hypofunction of ischemic brain, cerebral blood flow (CBF) dynamics and SEPs during induced-hypertension were measured before, during and after operation in 19 completed stroke patients with main trunk occlusion of MCA. As control studies, cerebral angiographies and CBF studies were performed in 29 conservatively treated cases. Furthermore, preoperative angiographical findings, STA-MCA shunt flow and blood pressure of STA and MCA were examined respectively in surgically treated cases. From these studies, our present criteria for bypass operation evolved as follows: 1) Mean CBF value is in 25 to 32 ml/ 100g/min without global loss of autoregulation and CO2-reactivity; 2) Amplitude of initial component of SEP is augmented 2 times or more during induced-hypertension than at rest state; 3) The N1-amplitude ratio of the normal side to the affected side is above 0.5 at rest state and increased approximately to normal value, i.e., 1.0 by induced-hypertension; and 4) The STA-MCA shunt flow through STA is in 40 to 90 ml/min and the MCA blood pressure is in 40 to 60 mmHg.