Diagnostic Efficacy of Mental Nerve SEP(Somatosensory Evoked Potentials) for the Injured Inferior Alveolar Nerve

Sensory dysfunction following the injury of the inferior alveolar nerve requires objective examination to get a reproducible data and to provide necessary treatment. This study was designed to evaluate if the SEP(somatosensory evoked potentials) of the mental nerve can be used as an objective method for the diagnosis of nerve injury and sensory disturbances. The subjects were nineteen patients (37.4+/-11.3 years old) who had been suffered from sensory disturbance of the unilateral lower lip and mental region for over 6 months after the inferior alveolar nerve injuries confirmed by the microsurgical explorations. The clinical neurosensory tests as SLTD(static light touch discrimination), MDD(moving direction discrimination), 2PD(two point discrimination), PPN(pin prick nociception) and accompanied pain were preceded to electro-physiologic examinations as SEP. The score of sensory dysfunction (sum score of all sensory tests) ranged from 0 to 8 were compared to the latency differences of the mental nerve SEPs. The correlation between clinical sensory scores and SEPs were tested by Spearman nonparametric rank correlation analysis, the differences in SEP latency by Kruskal-Wallis test and the latency differences according to PPN and accompanied pain by Mann-Whitney U test. This study resulted that the difference of the latencies between normal side and affected side was 2.22+/-2.46 msec and correlated significantly with the neurosensory dysfunction scores (p=0.0001). Conclusively, the somatosensory evoked potentials of the mental nerve can be a useful diagnostic method to evaluate the inferior alveolar nerve injuries and the change of sensory dysfunction to be reproduced as an objective assessment.

Intraoperative SSEP Monitoring during Aneurysm Surgery

Somatosensory evoked potential(SSEP) has been recorded during 31 operations for intracranial aneurysm. We had monitored the SSEP in each stage of aneurysm surgery(preoperative, anesthetic induction, dura opening, temporary vascular occlusion, aneurysm neck clipping and 30 minute after aneurysm neck clipping). Temporary occlusion of intracranial arteries have performed in 21 cases. In cortical amplitude of more than 50% as compared with induction was considered to be "significant" SSEP change. Eleven out of 21 cases of temporary vascular occlusion showed significant decrease of amplitude. Three out of 4 cases with flat wave had new neurologic deficits postoperatively. We studied the relationship between SSEP changes and postoperative neurologic deficit and concluded as follows: 1) The monitoring of amplitude of SSEP may help control the duration and number of application in temporary clipping during aneurysm surgery. 2) Decreased in amplitude with temporary clipping, especially flat wave, is a strong suggestion of the postoperative neurologic deficit. These results indicate that monitoring of SSEP during aneurysm surgery would be helpful to reduce the incidence of postoperative neurologic deficits.

Studies on the sensory changes and somatosensory evoked potential in thalamic stroke

BACKGROUND: The thalamus is a subcortical gray-matter composed of several groups of nuclei. Though there are some characteristic clinical findings in thalamic stroke syndrome, it is not easy to identify their own function in each nuclei. We demonstrated this study to figure out the relationships between anatomic nucleus, sensory symptoms, and electrophysiologic findings in thalamic stroke. METHODS: Sixteen thalamic stroke patients were studied. Fifteen cases showed thalamic lacunar infarction by magnetic resonance imaging and one case showed thalamic hemorrhage by computed tomography. We compared their sensory symptoms and signs, somatosensory evoked potentials(SSEP), the size of lesions, and the location of lesions on imaging studies. RESULTS: There were 12 cases of a lesion on ventroposterolateral(VPL) nucleus(Group I) and 4 cases of a lesion on the other nuclei(Group II). All 8 cases which had a sensory deficit in Group I, and 2 cases - one with sensory deficit and the other without in Group II, showed abnormal SSEP findings. There were 9 cases in Group I and 3 cases in Group II with thalamic pain and there was no relationship between SSEP and thalamic pain. Five were pure sensory strokes in 6 patients with a small lesion(less than 0.5 cm), and pure sensory strokes were only 3 in 10 patients with relatively a large lesion (between 0.5 and 1.5 cm). CONCLUSION: There was significant relationship between sensory deficit and SSEP. SSEP can be used as a objective method in estimating the sensory deficit of thalamic stroke. We could ascertain the fact that other nuclei as well as VPL nucleus were associated with the development of pain in thalamic stroke, and there was significant relationship between the size of lesion and the clinical feature of stroke.

The Effect of Somatosensory Evoked Potential by Stretching of Spinal Dura in the Dog / 대한정형외과학회잡지

Spinal instrumentation is popular nowadays. After applying the Harrington distraction rod, there might be a severe, tragic complication, paraplegia. Recently SSEP is widely used to detect the early change of the spinal cord dysfunction. The force to correct the spinal deformity is usually distraction. The distraction force will stretch the spinal dura. But the relation of neural deficit between distraction force and duration is not clearly determined yet. Also the anatomical level of neural deficit is not known. The purpose of this study is to find that the distraction force of 200gm on the spinal dura will change the SSEP by the stimulation of the posterior tibial nerve and if there is change of SSEP, what portion of nerve stimulation pathway is responsible for. Results are as followings. 1) The distraction force of 200gm makes change of SSEP wave. 2) P2 wave is most susceptible, N1 wave is less susceptible and P1 is relatively contant for one hour dural traction. 3) After release of traction, the wave is partially reversible but not completely for next one hour recovery period. 4) While the wave of SSEP is changed by the dural distraction force, the nerve conduction between the nerve root just outside of the spinal dura and calf shows constant latency. That means the anatomical level responsible for the change of SSEP wave is proximal to the spinal dura, not the peripheral nerve distal to the spinal dura.

A Case of Thoracic Meningomyelocele Containing Accessory Cord

The authors report a case of thoracic meningomyelocele. The patient had not have any presenting symptoms until adult age. We confirmed it with radiological(postmyelography CT and MRI) and pathological diagnosis. Pre-, post- and intraoperative SSEP(somatosensory evoked potential) monitoring were performed. Characteristically, the mass contained accessory cord which attached to inner cyst wall with multiple fibrous bands. Meningomyelocele was completely removed without any neurologic sequelae.

Relationship between SSEP and Vasospasm in SAH Patients

Cerebral vasospasm is one of most serious complication after subarachnoid hemorrhage due to aneurysmal rupture and a very important cause affecting to prognosis. The most reliable diagnostic assessment of cerebral vasospasm is angiography, but this is limited to perform because of complications such as neurological deficits or death, especially to repeat studdy. It seems likely that assessment of evoked elective, a much simpler and safer than the repeated study of angiography, will be of use in following the condition of patients with clinical vasospasm following SAH. In order to study relationship between clinical vasospasm and electrical activity, we traced SSEP from upper extremity by median nerve stimulation and lower extremity by posterior tibial stimulation which manifest the neurophysiologic function of cerebral ischemia. MN(Me-dian n.) and PTN(Posterior tibial n.)were performed simultaneously. Over 2 years period (1986 through 1988), 41 patients were performed SSEP and evaluated the relationship between SSEP and clinical or angiographic vasospasm in patients of SAH.

A Study on Somatosensory Evoked Potential in Patients with Cervical Spondylosis

In order to study the relationship between clinical group of cervical spondylosis and electrical activity, we traced somatosensory evoked potential(SSEP) by stimulating the median nerve(MN) from the upper extremities, and the posterior tibial nerve(PTN) from the lower extremities simultaneously. The purpose of this study was to test the clinical diagnostic utility of the method, whether any consistent relationship exists between the severity and type of neurological symptoms and the results of the SSEP responses, and between neurological improved patients after operation and improved SSEP results. In this study patients were clinically divided into three groups : combined myelopathy and radiculopathy, myelopathy alone, radiculopathy alone. Over a 3-year period from 1987 to 1989, SSEP were performed on 112 patients of Korean adults and summary of the results obtained are as follows : 1) Among patients with cervical spondylosis, those with cervical myelopathy showed more abnormal SSEP than those cervical radiculopathy. 2) In the group with myelopathy, MN-cervical latensy, Ep-C2 interpeak latency. PTN-P1 latency, and N1 latency were prolonged more than MN-C2 latency, Ep-C2 interpeak latency, PTN-P1 latency, and N1 latency of the group with radiculopathy. 3) The longer the duration of the symptoms, the more abnormal were the SSEP in patients with cervical spondylosis. 4) In patient with cervical myelopathy, the latency of SSEP was prolonged not only in those with sensory deficit, but also with motor deficit. 5) Half of clinically improved patients after operation showed improved SSEP in follow-up examinations. 6) Improvement in SSEP after operation was much affected by posterior approach.

Normal Data of Somatosensory Evoked Potential by Posterior Tibial Nerve Stimulation

This study was undertaken to obtain the normal somatosensory evoked potential pattern from stimulation of the posterior tibial nerve in order to provide basic data for clinical use in diagnosis and management of patients with brain and spinal cord lesions. Thirty-six patients, free of neurological disease and 14 volunteers were tested with 4-Channel Nicolet CA 1000 Clinical Averager. There were 26 male and 24 female, ranging in height from 156 to 178 centimeter, with a mean height of 165.2 centimeter. The results were as follows: 1) All lumbar waves(LP1, LN1) and early cortical waves(P1, N1, P2, N2) were easily identified in all of normal subjects, but P3 was obtaind in 52% of them. 2) Mean latency of each wave was P1(38.10msec.+/-2.23), N1(47.04msec.+/-2.18), P2(N59.98msec.+/-2.97), N2(76.48msec.+/-4.97), LP1(17.99msec.+/-1.75) and LN1(20.72msec.+/-1.53). 3) There was significant correlations between height of individuals and latency of the P1 and LP1. 4) Conduction time between LN1and P1 was 16.55msec. (1.03 and mean latency of left to right difference was 0.23msec.+/-0.19.

The Findings of Brainstem Auditory Evoked Pontential(BAEP) and Somatosensory Evoked Potential(SSEP) in Head Injury

There were 84 cases of brainstem auditory evoked potential(BAEP) and 90 cases of somatosensory evoked potential(SSEP) from the 124 cases of head injury. The studies were performed within the first three days after head injury in most cases and after ten days in emergency operative cases. The results of BAEP and SSEP studies recorded from 67 normal volunteers were used as a control group. The latency, amplitude and wave pattern of the evoked potential were examined and a peak or interpeak latency were considered abnormal when it exceeded the corresponding mean(2SD found in the control group. The wave patterns were arranged in BAEP as grade I:all waves were normal; grade II: waves I, II, III were abnormal;grade III:waves IV, V, VI were abnormal;grade IV:all waves were abnormal. In SSEP as grade I:all waves were normal;grade II:N13 wave was abnormal;grade III:N19wave was abnormal;grade IV:all waves were abnormal. The abnormal findings by percentage were:47.6% in latency of BAEP, 68.9% in latency of SSEP, 49.4% in wave pattern of BAEP and 87.8% in wave pattern of SSEP. The BAEP was superior to SSEP in correlation to clinical parameters including GCS, duration of coma, basal cisterns in initial brain CT scan and Glasgow outcome scale(GOS). As a BAEP criterion, the wave V latency and the BCT(III-V interpeak latency) and as a SSEP criterion, the central conduction time(N19-N13) were more correlated to duration of coma and GOS. The appearance of the basal cisterns on initial brain CT is significantly correlated with wave V and BCT of BAEP only. Grade I and II were reliable predictors of a good prognosis. Therefore, we concluded that BAEP and SSEP are adjunctively diagnostic tests for determining the outcome of head injuried patients.

Clinical Evaluation of Evoked Potentials in Cerebrovascular Diseases

With 4-Channel Nicolet-CA 1000 clinical averager, somatosensory evoked potentials(SSEP) and brainstem auditory evoked potentials(BAEP) were studied in 40 patients with intracerebral hematoma and 40 patients with cerebral infarction. SSEP was more sensitive response in putamen(20/23) or thalamic(6/7) hemorrhage and infarction of middle cerebral artery territory(13/28). in contrast BAEP was high percentage in abnormality in brainstem or cerebellar lesion. Cortical wave(N18) was usually not traceable in large size of hematoma or having midline shift in brain CT scan. There was close correlation between the severity of motor weakness and abnormality of SSEP. The best neurological outcome was found in the patients of P24 wave formation. In our results, SSEP and BAEP seemed to be very useful for evaluation of stroke patients.

Evoked Potentials in Brain Death

With 4 Channel Nocolet-CA 1000 clinical averager, somatosensory evoked potentials(SSEP), brainstem auditory evoked potentials(BAEP) and visual evoked potentials(VEP) were studied in 23 patients who fulfilled the clinical criteria for brain death. The results were as follows : 1) In SSEP, all patients had identifiable Erb's point wave and 11 out of 23 patients(48%) had cervical portion wave, but none of these patients had identifiable cortical portion wave. 2) In BAEP, 19 out of 23 patients(83%) had no identifiable BAEP waveforms, including wave I, and 4 patients(17%) had only wave I. 3) In VEP, 15 out of 23 patients(65%) had no identifiable VEP waveforms and 8 patients(35%) had short latency-low amplitude wave with no any of the longer latency components of central system origin.

Correlation of Evoked Potentials and Regional Cerebral Blood Flow in SAH Patients with Vasospasm

With 4 channel Nicolet-CA 1000 clinical averager and 133 Xenon inhalation method, somatosensory evoked potentials (SSEP), brainstem auditory evoked potentials (BAEP) and regional cerebral blood flow (r-CBF) were studied in 30 patients with ruptured cerebral aneurysms. 8 out of 30 patients had abnormal SSEP, 11 out of 30 patients had abnormal BAEP and 4 out of 14 patients had decreased r-CBF. The SSEP was abnormal in 6 out of 10 patients with severe vasospasm but in only 2 out of 20 patients without vasospasm or with mild and moderate spasm. The BAEP was abnormal in 5 out of 10 patients with severe vasospasm but 6 out of 20 patients without spasm or with mild and moderate spasm. Regional CBF was decreased in 3 out of 4 patients with severe vasospasm but only 1 out of 10 patients without spasm or with mild and moderate spasm. Abnormal SSEP, BAEP & decreased r-CBF in patients with severe vasospasm indicated a poor prognosis. We got the results as follows ; 1) Abnormal SSEP, BAEP and decreased r-CBF are correlated with severity of vasospasm in SAH patients. 2) Abnormal SSEP and BAEP correlated with the clinical status. 3) Brain stem transmission time (BTT) is less sensitive than central conduction time (CCT) as indicator of vasospasm.