Botulinum toxin type A reduces hyperalgesia and TRPV1 expression in rats with neuropathic pain.

OBJECTIVE: We aim to determine the effects of botulinum toxin type A (BTX-A) on the thresholds of pain and the expression of transient receptor potential vanilloid type 1 (TRPV1) in the dorsal root ganglion (DRG) in rats with neuropathic pain induced by selective ventral root transection (VRT). METHODS: Neuropathic pain was induced by transection of the lumbar 5 ventral root in male Sprague-Dawley rats. BTX-A or saline was administered to the plantar surface by subcutaneous injection. SB366791 (an inhibitor of TRPV1) was administered intraperitoneally. Behavioral tests were conducted preoperatively and at predefined postoperative days. The expression of TRPV1 was detected and quantified by immunohistochemistry and Western blotting at postoperative days 3, 7, 14, and 21. RESULTS: TRPV1 expression increased significantly in the L4 ∼5 dorsal root ganglia 7 days after L5 VRT compared with the sham-operated control (P < 0.05). This increase persisted for at least 21 days. The thresholds of foot withdrawal to mechanical and thermal stimulation decreased significantly as well. Subcutaneous injection of BTX-A significantly and dose-dependently reduced the expression of TRPV1 (P < 0.05) and partially reversed the pain thresholds. CONCLUSION: Upregulation of TRPV1 expression in the DRG is an important mechanism of neuropathic pain induced by the VRT. The analgesic effect of BTX-A is most likely mediated through reduction of TRPV1 expression in the nociceptors.

Sequelae of a left-sided parietal stroke: posterior alien hand syndrome.

Posterior alien hand syndrome is a new addition to a poorly understood group of movement disorders. Historically, anatomical lesions causing uncontrolled limb movement and a feeling of foreignness were found to be located in the corpus callosum or frontal lobe. Recent case reports, however, demonstrate the typical symptoms of alien hand syndrome with lesions located in the parietal/occipital lobes. Disturbance of normal function in these regions tends to produce less complex motor activity, such as hand levitation, along with a sensory component characterized by feeling of estrangement. We discuss a patient who presented with unusual symptoms following an outpatient procedure and was found to have posterior alien hand syndrome.

Acute cauda equina syndrome secondary to a lumbar synovial cyst.

Cauda equina syndrome is a well described state of neurologic compromise due to lumbosacral root compression. In most cases, it is due to a herniated disc, tumor, infection, or hematoma. We report a case of rapid lumbar synovial cyst expansion leading to acute cauda equina syndrome and compare it to similar cases in the literature. The patient is a 49-year-old woman with a history of chronic low back pain who developed cauda equina syndrome. Serial lumbar magnetic resonance imaging studies demonstrated a significant increase in the size of a lumbar synovial cyst over a 2 week interval. After an unsuccessful attempt to relieve her acute symptoms with computed tomography-guided cyst aspiration, an L4-5 posterior spinal decompression with excision of the synovial cyst was performed. Postoperatively the patient's perineal numbness, bladder incontinence, and associated pain complaints resolved. The only residual symptom at one month follow-up was continued numbness in the right lower limb in an L5 distribution. This report adds to 6 other well described similar cases found in the literature by illustrating several important points. First, a lumbar synovial cyst is a rare but possible cause of acute cauda equina syndrome. Second, magnetic resonance imaging is the test of choice to diagnose and characterize lumbar synovial cysts; serial imaging can detect fluctuations in cyst size. Third, percutaneous treatment of lumbar synovial cysts is variable in efficacy and proved to be unsuccessful in our patient. Finally, surgical management has shown high success rates for symptomatic cysts. Specifically, in the setting of acute cauda equina syndrome secondary to a lumbar synovial cyst, urgent surgical decompression has led to resolution of neurologic symptoms in most reported cases. A lumbar synovial cyst is an uncommon cause of acute cauda equina syndrome. Prompt diagnosis and treatment may lead to reduced morbidity associated with this condition.

The accuracy of ultrasound-guided and palpation-guided peroneal tendon sheath injections.

OBJECTIVE: The aim of this study was to describe and to validate an ultrasound-guided peroneal tendon sheath (PTS) injection technique and to compare the accuracy of ultrasound-guided vs. palpation-guided PTS injections in a cadaveric model. DESIGN: Twenty cadaveric lower limbs were injected with and without ultrasound guidance, using a different color of liquid latex for each injection technique. The injections were performed by a single investigator in a randomized order. Cadaveric specimens were dissected 1 wk later by a blinded investigator who graded injection accuracy on a 3-point scale (1, accurate; 2, partially accurate; 3, inaccurate). RESULTS: Ultrasound-guided injections were 100% (20 of 20) accurate whereas palpation-guided injections were 60% (12 of 20) accurate (P = 0.008). Six palpation-guided injections were partially accurate, and two were inaccurate. Two of the partially accurate and both of the inaccurate injections were intratendinous. CONCLUSIONS: In a cadaveric model, ultrasound-guided PTS injections are significantly more accurate than palpation-guided injections. When performing PTS injections, clinicians should consider ultrasound guidance to improve injection accuracy and minimize potential complications such as intratendinous injection.

Accuracy of palpation-guided and ultrasound-guided needle tip placement into the deep and superficial posterior leg compartments.

BACKGROUND: Invasive leg compartment testing may be performed to diagnose chronic exertional compartment syndrome. No prior study has assessed the accuracy of leg compartment needle tip access. PURPOSE: This study was undertaken to describe and determine the accuracy of palpation-guided and ultrasound-guided techniques for needle tip placement into the deep and superficial posterior leg compartments by a less experienced clinician and a more experienced clinician using a cadaveric model. STUDY DESIGN: Controlled laboratory study. METHODS: Twenty unembalmed adult lower limb cadaveric specimens were used for the study. Two investigators, a sports medicine fellow with 10 months of musculoskeletal ultrasound experience and a staff physiatrist with 3 years of musculoskeletal ultrasound experience, each performed 1 palpation-guided and 1 ultrasound-guided colored latex dye injection into the deep and superficial posterior leg compartments of each cadaveric specimen. A blinded investigator dissected the specimens and graded them for accuracy. RESULTS: The accuracy rates of palpation-guided (accuracy rate, 90%; 95% confidence interval [CI], 76%-97%) and ultrasound-guided (accuracy rate, 88%; 95% CI, 73%-95%) deep posterior compartment injections were statistically equivalent (P = 1.000). All 80 injections performed into the superficial posterior compartment were accurate (accuracy rate, 100%; 95% CI, 89%-100%). The accuracy of the less experienced investigator (total injection accuracy rate, 88%; 95% CI, 73%-95%) and the more experienced investigator (total injection accuracy rate, 90%; 95% CI, 76%-97%) were not significantly different (P = 1.000). CONCLUSION: Needle tip placement into the deep and superficial posterior leg compartments is relatively accurate with palpation guidance regardless of level of experience, and does not improve with the use of ultrasound guidance. CLINICAL RELEVANCE: Ultrasound guidance does not appear to be indicated for routine deep or superficial posterior leg compartment pressure testing. However, this does not preclude the need for ultrasound guidance in selected clinical scenarios.

Postoperative pericardial adhesion prevention using Carbylan-SX in a rabbit model.

INTRODUCTION: The presence of dense adhesions within the pericardial space complicates reoperative cardiac surgery. Prior attempts to reduce adhesion formation after primary cardiac surgery using medications or biomaterials have had variable success. Carbylan-SX (Carbylan Biosurgery Inc., Palo Alto, CA) is a hyaluronan-based biomaterial, which has been shown to be effective at reducing adhesions in a nonthoracic rat model. This study evaluates whether Carbylan-SX can effectively reduce postoperative adhesions within the pericardial cavity. METHODS: Thirty-eight New Zealand white rabbits underwent a left lateral thoracotomy. A pericardiotomy was made and epicardial adhesions were induced on the anterior surface of the heart using a Dremel device (Racine, WI). The rabbits were divided into four groups: controls with abrasions only receiving no treatment (n=10), Carbylan-SX films (n=10), Carbylan-SX aerosolized hydrogel (n=10), and Seprafilm (n=8). The pericardial sac and chest were subsequently closed. Rabbits were sacrificed at a mean of 15 days. For histological analysis, each heart was divided into 12 separate 1 mm sections. Computer imaging software was used to measure the adhesion thickness and the mean of 12 random measurements for each animal was recorded and statistical analysis performed. RESULTS: Histological analysis revealed all treatment groups to be significantly better than the control (2159 mum thickness, P<0.0001) at preventing adhesions. The Carbylan-SX film and Carbylan-SX aerosolized hydrogel both proved to be better at preventing adhesions than Seprafilm (Genzyme Corp., Cambridge, MA) with an average adhesion thickness of 454 and 577 microm, respectively, compared with 1319 microm for Seprafilm (P<0.0001 and P<0.0005, respectively). The Carbylan-SX film and Carbylan-SX aerosolized hydrogel were equally effective at preventing adhesion formation. CONCLUSION: Carbylan-SX film and Carbylan-SX aerosolized crosslinkable hydrogel are equally effective methods of reducing postoperative pericardial adhesions within the pericardial cavity. Both the Carbylan-SX film and aerosolized hydrogel showed a significantly greater reduction in adhesions than Seprafilm. Clinical application of Carbylan-SX could have significant therapeutic implications in the future.