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Biomedical subjects

Michael J Dorsi

Publications and source records attributed to Michael J Dorsi.

6 recordsLinked to original sources
PubMed2005

Spinal cord stimulation electrode design: a prospective, randomized, controlled trial comparing percutaneous with laminectomy electrodes: part II-clinical outcomes.

OBJECTIVE: Spinal cord stimulation, in use for more than 30 years, has evolved into an easily implemented technique involving percutaneous or laminectomy electrode placement. In a randomized comparison of four-contact percutaneous and four-contact insulated laminectomy electrodes placed at the same level in the dorsal, epidural midline, quantitative measures of stimulator performance revealed significant technical advantages for the laminectomy electrodes. Our prospective, randomized, controlled trial compares clinical results in these same patients. METHODS: Impartial third parties followed our series of 24 patients with failed back surgery syndrome to gather clinical outcome data. We defined "success" as at least 50% sustained relief of pain and patient satisfaction with the result of treatment. RESULTS: At a mean follow-up of 1.9 years, 10 of 12 patients receiving the laminectomy electrode and 5 of 12 patients receiving the percutaneous electrode reported a successful outcome (P < 0.05). Follow-up at a mean of 2.9 years showed that this result was maintained in 5 of 12 patients with the laminectomy electrode and 3 of 12 with the percutaneous electrode (not statistically significant). Many patients reported improvements in most activities of daily living, and loss of function was rare. In addition, 9 patients with laminectomy electrodes and 4 with percutaneous electrodes reducted or eliminated analgesic intake (P < 0.05), and 2 returned to work. No electrode migration was observed. CONCLUSION: Laminectomy electrode placement, although more invasive than percutaneous placement, yields significantly better clinical results in patients with failed back surgery syndrome at mean 1.9 years follow-up. In our small sample, however, the statistical significance of this advantage disappeared at mean 2.9 years follow-up.

Adult↗
PubMed2004

Paraspinal nerve sheath tumors.

Spinal tumors compose a vast heterogeneous group of neoplasms that are classified by origin into vertebral column, spinal canal, or paraspinal region tumors. Tumors with both intraspinal (intracanalicular) and paraspinal (extracanalicular) components that communicate via an intravertebral foramen are defined as "dumbbell tumors." This article focuses on the characteristics of a few types of paraspinal tumors, with special emphasis on the management of nerve sheath dumbbell tumors.

Humans↗
PubMed2004

Surgical repair of brachial plexus injury: a multinational survey of experienced peripheral nerve surgeons.

OBJECT: Brachial plexus injuries (BPIs) are often devastating events that lead to upper-extremity paralysis, rendering the limb a painful extraneous appendage. Fortunately, there are several nerve repair techniques that provide restoration of some function. Although there is general agreement in the medical community concerning which patients may benefit from surgical intervention, the actual repair technique for a given lesion is less clear. The authors sought to identify and better define areas of agreement and disagreement among experienced peripheral nerve surgeons as to the management of BPIs. METHODS: The authors developed a detailed survey in two parts: one part addressing general issues related to BPI and the other presenting four clinical cases. The survey was mailed to 126 experienced peripheral nerve physicians and 49 (39%) participated in the study. The respondents represent 22 different countries and multiple surgical subspecialties. They performed a mean of 33 brachial plexus reconstructions annually. Areas of significant disagreement included the timing and indications for surgical intervention in birth-related palsy, treatment of neuroma-in-continuity, the best transfers to achieve elbow flexion and shoulder abduction, the use of intra- or extraplexal donors for motor neurotization, and the use of distal or proximal coaptation during nerve transfer. CONCLUSIONS: Experienced peripheral nerve surgeons disagree in important ways as to the management of BPI. The decisions made by the various treating physicians underscore the many areas of disagreement regarding the treatment of BPI, including the diagnostic approach to defining the injury, timing of and indications for surgical intervention in birth-related palsy, the treatment of neuroma-in-continuity, the choice of nerve transfers to achieve elbow flexion and shoulder abduction, the use of intra- or extraplexal donors for neurotization, and the use of distal or proximal coaptation during nerve transfer.

Activities of Daily Living↗
PubMed2002

Mechanical hyperalgesia after an L5 ventral rhizotomy or an L5 ganglionectomy in the rat.

An L5 spinal nerve ligation (SNL) in the rat leads to behavioral signs of mechanical hyperalgesia. Our recent finding that an L5 dorsal root rhizotomy did not alter the mechanical hyperalgesia following an L5 SNL suggests that signals originating from the proximal stump of the injured nerve are not essential. We postulate that Wallerian degeneration of L5 nerve fibers leads to altered properties of adjacent intact nociceptive afferents. To investigate the role of degeneration in sensory versus motor fibers, five injury models were examined concurrently in a blinded fashion. An L5 ganglionectomy produced a selective lesion of sensory fibers. An L5 ventral root rhizotomy produced a selective lesion of motor fibers. The three control lesions included: (1) SNL with L5 dorsal root rhizotomy; (2) L5 dorsal root rhizotomy; and (3) exposure of the L5 roots without transection (sham). Paw withdrawal thresholds to mechanical stimuli were measured at three sites in the rat hindpaw corresponding to the L3, L4, and L5 dermatomes. Both the ganglionectomy and the ventral rhizotomy produced a significant, lasting (>or=20 d) decrease of mechanical withdrawal thresholds that was comparable to that produced by the SNL lesion. The L5 dorsal rhizotomy, by itself, produced a short lasting (<or=6 d) decrease in thresholds, whereas the sham procedure did not produce a significant change. We propose that interactions between degenerating motor and sensory fibers of the injured nerve and intact afferent fibers of neighboring nerves play a critical role for both initiation and maintenance of mechanical hyperalgesia in neuropathic pain.

Animals↗
PubMed2000

Mechanical hyperalgesia after an L5 spinal nerve lesion in the rat is not dependent on input from injured nerve fibers.

An injury to a peripheral nerve in animals often leads to signs of neuropathic pain including hyperalgesia to heat, cold and mechanical stimuli. The role of injured and intact nerve fibers in mechanical hyperalgesia was evaluated in rats subjected to an L5 spinal nerve ligation-and-cut ('modified SNL lesion'). To assess the contribution of injured afferents, an L5 dorsal rhizotomy was performed immediately before, or 7 days after the modified SNL lesion. To study the role of adjacent intact spinal nerves, an L4 dorsal rhizotomy was performed 7 days after the modified SNL lesion. The up-down method of Dixon (Dixon WJ, Annu Rev Pharmacol Toxicol 1980;20:441-462) was used to measure the paw withdrawal threshold to mechanical stimuli at three sites on the rat hindpaw corresponding to the L3, L4, and L5 dermatomes. We found that the modified SNL lesion produced a significant, lasting (20 days) decrease of the mechanical withdrawal threshold. The severity and duration of mechanical hyperalgesia varied across testing sites. The L5 and L4 dermatome test sites developed the most severe and lasting mechanical hyperalgesia. In contrast, the L3 testing site developed significantly less severe and shorter lasting mechanical hyperalgesia. L5 dorsal rhizotomy, by itself, produced a transient decrease in mechanical withdrawal thresholds. L5 dorsal rhizotomy performed before, or 7 days after, the modified SNL lesion did not prevent or resolve the observed decrease in mechanical withdrawal thresholds. L4 dorsal rhizotomy performed 7 days after the modified SNL lesion resulted in an immediate reversal of mechanical withdrawal thresholds back to baseline values. These results suggest that, after L5 spinal nerve ligation-and-cut, mechanical hyperalgesia develops and persists independent of input from injured afferents. We propose that the Wallerian degeneration that develops after a nerve injury leads to interactions between the degenerating fibers of the injured spinal nerve and the intact fibers of adjacent spinal nerves. This leads to changes in the intact fibers that play a critical role for both initiation and maintenance of mechanical hyperalgesia.

Animals↗