Paraparesis due to pressure erosion of the thoracic spine by an aortic aneurysm: remission of symptoms following resection of the aneurysm and vertebral reconstruction.

BACKGROUND: There are only a few descriptions in the literature of thoraco-abdominal aortic aneurysms responsible for erosion of the vertebral column and compression of the spinal cord. This case is therefore presented to provide an opportunity to discuss the pathomechanic aspects and to demonstrate the feasibility of total surgical repair by an interdisciplinary approach. METHODS: A thoraco-abdominal aortic aneurysm caused extensive erosion of vertebral bodies T5-8, leading to invasion of the spinal canal and compression of the cord. The clinical signs were paraparesis and chronic thoracolumbar pain. In a combined operation the aneurysm was replaced by a Dacron prosthesis. Corpectomy of T5-8 was carried out and a titanium mesh cage filled with autogenous bone tissue was inserted. The vertebral column was stabilized using dorsal and lateral instrumentation. FINDINGS: Clinical and imaging follow-up after three years showed remission of the patient's severe paraparesis and chronic pain and long-term technical success of the vertebral and aortic reconstruction. INTERPRETATION: Complete thoraco-abdominal aortic replacement and spinal column repair can be successfully accomplished with good clinical and neurological long-term results.

[Treatment of spinal fracture in ankylosing spondylitis]. / Behandlung der Wirbelsäulenfraktur bei ankylosierender Spondylitis.

Clinical guidelines for the treatment of vertebral fractures associated with ankylosing spondylitis are derived from case reports and a review of literature. The coincidence of paravertebral calcifications and fracture formations leads to problems in the establishment of a proper initial diagnosis. Therefore computed tomography and magnetic resonance imaging have to be employed to define the extent of fracture and the presence of spinal lesions. As a rule vertebral fractures based upon spondylitic alterations are extremely unstable and tend to secondary dislocation with a high risk of spinal cord injuries. Operative osteosynthesis is the method of choice in the fracture treatment. A successful stabilization requires an extended spondylodesis comprising at least five vertebral segments by a dorsal or a combined ventral instrumentation.

Enlargement of a chronic aseptic lumbar epidural abscess by intraspinal injections--a rare cause of progressive paraparesis.

The frequent use of invasive procedures at the spinal cord such as epidural injections has led to an increased incidence of iatrogenic abscesses. We report the case of a patient who suffered from low back pain. During epidural lumbar injections of steroids the patient developed severe radicular symptoms, resulting in severe paraparesis. We demonstrate the rare cause of this progressive deterioration, being a combination of a preexisting chronic aseptic epidural abscess and an iatrogenic enlargement by repeated epidural injections. MR-Scans demonstrated a mass lesion at the L4/5 vertebral level, which was surgically removed. Histological evaluation revealed the presence of a chronic aseptic spinal epidural abscess with acute bleedings. Histology and MR-Data disclosed multiple deposits of the applied drug within the abscess and in the surrounding paravertebral soft tissue. The authors prove that the cause of the neurological deterioration was due to epidural injections into a preexisting lumbar chronic aseptic epidural abscess. Harmful and unpleasant complications may occur following epidural injections. Though we present a very rare cause of such complications, a careful monitoring of the neurological status of the patient is necessary as well as the early application of MR imaging in the case of deterioration.

Spinal cord and nerve root monitoring in spine surgery and related procedures.

Intensive research in the field of intraoperative neurophysiologic monitoring has been performed directed at finding reliable stimulating and recording techniques and adequate anesthetic regimes applicable to spinal procedures. The aim is a comprehensive monitoring not only of afferent and efferent spinal cord pathways but also of sensory and motor nerve roots and cauda equina fibers. Conventional somatosensory evoked potentials (SEPs) are complemented by motor evoked potentials, dermatomal sensory evoked potentials, spinal cord evoked potentials, evoked electromyography, sensory and motor fiber mapping of the cauda equina, bulbocavernosus reflex testing, and neurogenic evoked potentials. Apart from describing the essentials of these techniques and their indications and limitations, this article deals with the influence of anesthetic management on the production and interpretation of evoked potentials.

Speed and pressure characteristics of external anal sphincter contractions.

The principle of isochronism reflects constant contraction time for varying strengths of muscle contraction. This principle was studied for the innervation of the pelvic floor in humans using motor-evoked potentials (MEPs) and evoked pressure curves (EPCs) from the external anal sphincter muscle (EAS). MEPs and EPCs were simultaneously recorded after transcranial magnetic stimulation of the motor cortex. Voluntary contractions were also studied. Contraction times of the EAS were significantly longer in voluntary contractions (mean, 237 ms) than in EPCs (mean, 90 ms). Depending on either mode of contraction, contraction times varied only slightly despite a wide range of contraction strengths. It is shown that the contractile behavior of the EAS is a function of slow- and fast-twitch muscle fiber distribution and that the principle of isochronism governs motor performance not only of limb muscles but also of the EAS. There exists a unique optimal working range of each muscle to meet its individual function. Disturbance of this principle results in a less efficient contraction with either inappropriate basic tone or disturbed reflex activation in the EAS. Both are possible causes of incontinence.

Neurophysiological techniques in the evaluation of disorders of the spine.

Neurophysiological investigations are indispensable tools in evaluating and quantifying functional impairment of spinal cord structures and adjacent nervous tissue in any disorder of the spine accompanied by neurological symptoms. In this review the relevant neurophysiological techniques will be briefly described and their differential value for diagnosis and prognosis of spinal cord damage discussed. Typical case reports of spine disorders at different spinal levels are presented to illustrate results and interpretations of neurophysiological investigations.

Magnetic stimulation for monitoring of motor pathways in spinal procedures.

Transcranial magnetic stimulation was used for intraoperative motor evoked potential monitoring during surgery of intramedullar, extramedullar, and extradural spinal tumors in 13 patients. Anesthesia was based on etomidate. Magnetic stimulation for motor evoked potential monitoring was successful in 10 of 13 patients, 12 of whom were neurologically impaired. Motor evoked potentials were recorded from limb muscles or from the fibers of the cauda equina. Amplitudes of baseline recordings (the initial recording obtained after induction of anesthesia) were decreased by 64 +/- 34% (mean +/- SD) and baseline latencies were increased by 7 +/- 8% compared with the preoperative recordings. Subsequent recordings were analyzed for amplitude and latency changes in comparison to baseline. Amplitude changes exceeding 50% and latency changes higher than 3 ms compared with the baseline correctly indicated an impending lesion of motor pathways with increased paresis postoperatively. In cases where motor evoked potential monitoring was successful prediction of short-term postoperative motor outcome was always correct. There were no "false-negatives" or "false-positives."

Neurophysiological evaluation of disorders and procedures affecting the spinal cord and the cauda equina.

Neurophysiological tests that asses afferent or efferent pathways of the spinal cord and of nerve roots are used for clinical diagnosis, intraoperative monitoring, and judgement of prognosis. Most tests can readily be performed in awake subjects, whereas many difficulties arise in anesthetized patients in whom neurophysiological testing is the only way of monitoring functional integrity of neural tissue. The research, therefore, that has been carried out in this field during the past year is of special interest.

Motor evoked potentials in patients with spinal disorders: upper and lower motor neurone affection.

Motor evoked potentials (MEP) following magnetoelectric stimulation allow for detection and quantification of a lesion of the central and peripheral motor pathways. MEP latency is a very sensitive parameter, irrespective whether the lesion affects the upper motor neurone, e.g. in cervical myelopathy, or the lower motor neurone e.g. in cervical or lumbar radiculopathy. However, an increase of MEP latency alone does not allow for a distinction of either upper motor neurone or lower motor neurone affection. We have therefore scrutinized MEP latency and MEP waveform (amplitude, duration, and number of phases) in normal subjects, as well as in patients with cervical myelopathy (upper motor neurone affection: UMNA) and in patients with radiculopathies (lower motor neurone affection, LMNA). The increase of central motor latency compared to normal values was significantly higher in UMNA than in LMNA. MEP following transcranial magnetoelectric stimulation were split up and their duration in relation to M-wave duration was significantly increased in patients with UMNA, yet normal in patients with LMNA. MEP amplitude in relation to M-wave amplitude was significantly decreased in patients with UMNA, yet normal in patients with LMNA. We conclude that cervical myelopathy and cervical or lumbar radiculopathies lead to changes of MEP waveform, which are specific for either upper or LMNA. The analysis of amplitude, duration, and number of phases of MEP following transcranial stimulation increases the diagnostic value of MEP in disorders of the spine affecting the central or proximal peripheral motor pathways.

Magnetic stimulation of motor cortex and motor roots for painless evaluation of central and proximal peripheral motor pathways. Normal values and clinical application in disorders of the lumbar spine.

Magnetic stimulation of the motor cortex, motor roots, and proximal nerve trunks was performed in 46 healthy adults and in 73 consecutive patients with disorders of the lumbar spine. In combination with neurography and F-wave recordings, the fractionated stimulation of the motor pathways allowed calculation of conduction times of the pyramidal tract fibers, of the motor roots (ie, caudal fibers), and of the motor fibers of the lumbosacral plexus. Normal values for motor conduction times to the quadriceps, anterior tibial, and extensor digitorum brevis muscles were established. Patients had clinical and radiologic diagnoses of spinal stenosis (n = 43) and nerve root compression syndromes (n = 30). Motor conduction times to lower limb muscles were significantly delayed (above mean normal value +/- 2 x SD) in 65% of the patients with spinal stenosis and 50% of the patients with nerve root compression syndromes. Conduction slowing could be localized within the motor root and caudal fiber segment of the motor pathways in 80% of the patients in whom F-waves could be recorded. This method can be used to verify, quantify, and locate lesions of the motor pathways in conditions such as compression of the spinal cord, the caudal fibers (spinal stenosis), or the motor root passing through the intervertebral canal.

Quantification of motor pathways to the pelvic floor in humans.

The motor innervation of the pelvic floor plays a major role in defecation disorders such as fecal incontinence. It consists of central motor pathways and peripheral nerve fibers. Transcranial magnetoelectric stimulation of the brain and magnetoelectric stimulation of the lumbosacral motor roots were performed in 10 healthy volunteers. Motor evoked potentials were recorded from the external anal sphincter. This procedure allowed differentiation between a predominantly central and a solely peripheral component of the motor innervation of the external and sphincter. To compare these recordings with well-established data, motor evoked potentials were also recorded from the anterior tibial muscle. The central motor conduction time was 20.9 +/- 2.4 ms to the external anal sphincter and 14.8 +/- 2.3 ms to the anterior tibial muscles. Central motor conduction velocities were 40.7 +/- 5.2 and 55.5 +/- 7.6 m/s, respectively. This showed that conduction in the central fibers to the external anal sphincter was significantly slower than in those to the anterior tibial muscle. We conclude 1) that magnetoelectric stimulation allows differentiation between central and peripheral portions of the motor innervation of the pelvic floor, and 2) that central motor pathways innervating the pelvic floor differ significantly in their physiological properties from those innervating limb muscles.

Conduction velocities of pyramidal tract fibres and lumbar motor nerve roots: normal values.

Measurements of spinal cord and individual lumbar nerve root lengths were performed in 20 dissected cadavers. These data were correlated with the pyramidal tract and motor root conduction times obtained in 53 healthy subjects using motor evoked potentials. The distance between motor cortex and the level of the anterior horn cells ranged from 50.2 +/- 3.0 cm (mean +/- standard deviation) for the L1 segment to 54.4 +/- 3.6 cm for the L5 segment. The length of the motor roots from their exit from the myelon to their exit from the intervertebral foramen ranged from 10.3 +/- 1.7 cm in the L1 root to 17.5 +/- 1.9 cm in the L5 root. The central motor conduction velocity calculated for the distance motor cortex - anterior horn cells of the L5 segment was 50.1 +/- 4.5 m/s. The proximal peripheral conduction velocity of the motor nerve root between its exit from the spinal cord and its exit from the intervertebral foramen was 75.9 +/- 29.0 m/s. The overall conduction velocities between motor cortex and exit of the nerve roots from the intervertebral foramen were 57.4 +/- 6.3 m/s for the L4 fibers to the quadriceps femoris and 57.3 +/- 6.1 m/s for the L5 fibers to the anterior tibial muscle.

[Intraoperative monitoring with evoked potentials in spinal interventions]. / Intraoperatives Monitoring mit evozierten Potentialen bei spinalen Eingriffen.

This review article delineates the physiology and methodological principles of somatosensory (SEP) and motor evoked potentials (MEP), as well as our own results in 40 patients monitored during spinal surgery. In 29 patients an intraoperative SEP and in 15 patients a MEP monitoring was performed. Both modalities were applied in 4 patients. 19 patients had an intramedullary tumor, 15 patients had an intradural extramedullary tumor, 4 patients had an extradural mass lesion, and 2 patients had a spinal arteriovenous malformation. Technical problems with SEP monitoring occurred in 3 of 29 cases, problems with MEP monitoring occurred in 4 of 15 cases. Whereas anesthesia showed only little influence on SEP, an appropriate anesthesiological management was of major importance for MEP monitoring. Other factors, e.g. body temperature and blood pressure, also affected the evoked potentials. In all 35 patients in whom intraoperative SEP and/or MEP monitoring was successfully performed, evoked potentials showed a clear correlation with the initial postoperative neurological findings i.e. there were only cases of correct positive or correct negative monitoring. Transient evoked potential changes could always be attributed to surgical maneuvers. Our results show that intraoperative spinal cord monitoring with both SEP and MEP can supply helpful information on neural integrity. The choice of the evoked potential modality to be used and the choice of the sites of stimulation and recording depends on individual pathoanatomical findings and on the operative procedure required. Intraoperative evoked potential monitoring is indispensable during high risk spinal surgery such as surgery for intramedullary tumor or for mass lesions above C5.

Motor-evoked potentials in patients with cervical spine disorders.

Measurements of motor-evoked potentials by means of fractionated magnetic stimulation of motor pathways to the upper limbs was performed as part of the clinical assessment in 268 patients with cervical spine disorders. Seventy-two percent of the 127 patients with degenerative changes of the cervical spine, 67% of the 55 patients with rheumatoid arthritis (RA), and 57% of the 51 patients with trauma of the cervical spine showed a pathologic delay of central motor latency (CML). The data suggest that this method has a high sensitivity and therefore is recommended in the diagnosis of cervical spine disorders in patients with suspected compression of neural structures.

[Is transcranial magnetic stimulation a helpful method in diagnosis of cervical myelopathy in patients with chronic polyarthritis?]. / Ist die transkranielle Magnetstimulation eine hilfreiche Methode in der Diagnostik der zervikalen Myelopathie bei Patienten mit chronischer Polyarthritis?

Fifty-seven patients with rheumatoid arthritis were examined clinically, radiologically, and by means of transcranial magnetic brain stimulation. With this method central motor conduction times of the corticospinal pathways can be measured. The aim of the study was to compare the different methods to detect a cervical myelopathy and to correlate them. In 90% of patients clinical signs of cervical myelopathy could be detected, although in two-thirds of these, the neurological deficit was minimal. Radiologically, over 50% of patients had an atlanto-axid dislocation (AAD) of more than 5 mm. The central motor latencies measured in the upper extremities were prolonged in 47% of cases. These results show the usefulness of transcranial magnetic brain stimulation as an additional noninvasive investigation for detecting compression of the cervical myelon. This is an additional useful criterion for determining the need for operative intervention.

Clinical use of the magnetic stimulator in the investigation of peripheral conduction time.

The application of rapidly changing magnetic fields (magnetic stimulation) over the neck or lower back elicits EMG responses in the muscles of the arm or leg respectively. Such responses have stable onset latencies but their amplitudes vary depending on the position of the coil over the neck or lower back. Supramaximal responses could not be obtained. Comparison of onset latencies with estimates of peripheral conduction time using a conventional F-wave technique suggest that the site of excitation of the motor axons is about 1.3 msec conduction time distal to the cervical motoneurons and 3 msec distal to the lumbosacral motoneurons. Response configuration after paravertebral magnetic stimulation was similar to that of the standard electrically evoked M-wave in the small hand muscles but not in lower limb muscles. Responses in lower limb muscles after paravertebral magnetic stimulation may consist of additional F-wave and H-reflex components. The possible clinical role of paravertebral magnetic stimulation in the investigation of peripheral and central motor pathways is discussed in the light of these findings.

Magnetic transcranial brain stimulation: painless evaluation of central motor pathways. Normal values and clinical application in spinal cord diagnostics: upper extremities.

Painless transcranial magnetic stimulation has been performed on 53 healthy adults in order to obtain normal values of central motor pathway conduction times to cervical segments innervating upper limb muscles. Central motor latency was 5.1 msec when recording from the biceps brachii and 5.2 msec when recording from the abductor pollicis brevis or abductor digiti minimi muscles. The plexus motor latency as the conduction time between the cervical motor root and the proximal nerve trunks in the axillary region was 2.2 msec and 2.6 msec when recorded from the abductor pollicis brevis and abductor digiti minimi muscles, respectively. Conduction times higher than mean latency + 2 standard deviation may indicate a pathologic conduction slowing. Magnetic stimulation of the motor system is a new painless neurophysiologic technique enabling examination of the central motor pathways in awake subjects. With respect to spinal cord diagnostics, this method is useful in conditions such as compression of the spinal cord or of the motor root in the intervertebral foramen or canal.

Enprostil reduces the increase of gastric corpus mucosal mass induced by the hydrogen-potassium-stimulated adenosine triphosphatase inhibitor BY 831-78 in the rat.

We studied whether enprostil, a synthetic prostaglandin E2 derivative, might inhibit gastrin release and the trophic effects on gastric oxyntic mucosa induced by prolonged treatment with an inhibitor of hydrogen-potassium-stimulated adenosine triphosphatase, the substituted benzimidazole BY 831-78. Rats were treated intragastrically with enprostil (1 or 15 micrograms/kg b.i.d.), BY 831-78 (15 mumol/kg once daily), the combination of enprostil and BY 831-78, ranitidine (300 mumol/kg b.i.d.), and placebo. Plasma gastrin and somatostatin levels and gastric acid secretion were measured during a 1-day treatment in animals fitted with chronic gastric fistulas and repeatedly during 9 wk of treatment in intact rats. Despite inhibiting acid secretion, enprostil did not increase plasma gastrin. When combined with BY 831-78, enprostil transiently reduced the BY 831-78-induced increase of integrated plasma gastrin (1375 +/- 206 vs. 2137 +/- 256 pmol/L.12 h, p less than 0.05) in fasted rats with fistulas, but failed to prevent the marked hypergastrinemia following 9 wk of treatment with BY 831-78 (717 +/- 80 vs. 731 +/- 56 pmol/L) in intact rats. However, enprostil reduced the BY 831-78-induced increase of oxyntic mucosal volume (458 +/- 31 vs. 567 +/- 33 mm3, p less than 0.01), whereas BY 831-78 prevented the enprostil-induced increase of antral mucosal volume (42 +/- 3 vs. 56 +/- 3 mm3, p less than 0.01). These results demonstrate that some of the trophic effects induced by a hydrogen-potassium-stimulated adenosine triphosphatase inhibitor are not exclusively governed by gastrin.