Correlation analysis of somatosensory evoked potential waveforms: clinical applications.

OBJECTIVE: To assess the validity of the correlation coefficient (CC) as a diagnostic tool in evaluating somatosensory evoked potential (SEP) waveforms. DESIGN: SEP waveforms were recorded over the spine and scalp in response to tibial nerve stimulation at the ankle for 30 patients. SETTING: A general community, ambulatory, private referral center. PATIENTS: Patients were all ambulatory and were selected randomly from among existing patient records at the medical center. MAIN OUTCOME MEASURE: The test for validity uses the CC to verify reproducibility. The test for side-to-side symmetry uses the CC to obtain a measure of similarity between left and right tibial scalp responses. For both tests, a table is presented with CCs for normal subjects. If the CC for each patient falls below the appropriate critical value from the table, then the CC is taken to be abnormal; p values are provided at specific levels in this table. RESULTS: A new data base for the means and critical values of CCs with corresponding p values is established for normal subjects. Most of the patient data reveal significant CC nonreproducibility and lack of symmetry in tibial scalp SEP waveforms. CONCLUSION: The CC provides objective and quantitative waveform information that complements latency and amplitude measurements in the clinical interpretation of tibial scalp SEP waveforms.

Correlation analysis of somatosensory evoked potential waveforms.

Somatosensory evoked potential (SEP) waveforms were recorded over the spine and scalp in response to tibial nerve stimulation at the ankle for 28 subjects. The scalp data were analyzed with the correlation coefficient (CC) to determine the reproducibility of the signals and to identify side-to-side symmetry. The test for reproducibility uses the CC to verify validity, a low CC implying that the data are defective. The symmetry test uses the CC to obtain a measure of similarity of the responses to stimulation from opposite sides of the body. Statistics are presented showing the normal ranges of the CC values and their standard deviations. We conclude that the CC can provide objective and quantitative waveform information that complements latency and amplitude measurements in the clinical interpretation of tibial SEP waveforms.

Nerve injury complications. Management of neurogenic pain syndromes.

Postural brachial plexus compression neuropathy occurs more frequently than usually realized. The cause is multifactorial with certain predisposing anatomic and congenital factors that are not uncommon. An inciting event is required to cause a clinically significant syndrome. The event can be a specific traumatic episode or cumulative trauma leading to an adoption of a guarding posture, which results in a self-perpetuating cycle and brachial plexus nerve compression. The diagnosis and management may be complicated by concurrent vascular compression, concurrent reflex sympathetic dystrophy, and associated inflammatory musculotendinous conditions. Diagnosis relies on the appreciation of a peculiar symptom complex of pain and paresthesias. The important clinical signs are a supraclavicular Tinel's sign and a positive stress abduction test. Treatment includes exercises, patient education, and behavior modification. However, misdiagnosis can lead to inappropriate treatment, such as unnecessary carpal and cubital tunnel releases. Operative treatment is reserved for those severe cases that are resistant to extended and intense physical therapy. The preferred surgical technique involves an anterior, supraclavicular approach allowing for complete visualization and release of intrinsic and extrinsic nerve compression. Awareness is the key to making the diagnosis, and successful treatment requires a multidisciplinary approach. It is generally accepted that injuries to peripheral nerves result in serious losses of function. Paresthesias and motor weakness cause immediate functional limitation, and place the hand at risk for further injury. The system has little regenerative capacity, and the chance for recovery is poor even under the best circumstances. Therefore the treatment of acute nerve injuries can be difficult and frustrating.(ABSTRACT TRUNCATED AT 250 WORDS)

Intravasation of fat from the bone marrow cavity.

Fat labeled with triolein-(131)I was introduced through a burr hole into single tibial marrow cavities and the hole was sealed. The radioactivity over the thorax was monitored for 2-5 hours. After sacrifice, the radioactivity was determined in lungs, injected tibia or leg, kidneys, brain, thyroid gland and blood. Presence of pulmonary embolic fat was verified by histologic methods. Intravasation occurred after closure of the burr hole; it was delayed in several animals and failed to occur in 1 animal. The following mean percentages of the injected activity were found: in lungs 44.8% (0.04-85.1%); in tibia 44.7% (7.1-96.8%); in other investigated tissues and organs collectively, less than 1%. In another group, the tibia was fractured either immediately after injection of the labeled fat and closure of the burr hole, or while intravasation was in progress. After 2-5 hours, the lungs contained 23.2% (0.1-65.6) of the labeled fat, which was significantly less than in animals without fracture. In 2 animals, the needle was sealed into the burr hole, and the pressure necessary to produce intravasation was measued. A pressure of 50-100 mm of H(2)O produced pulmonary fat embolism as rapidly as the fat was injected.