Traumatic and iatrogenic sciatic nerve injury in 38 dogs and 10 cats: Clinical and electrodiagnostic findings.

BACKGROUND: Reports describing sciatic nerve injuries (SNI) and their outcome are scarce in veterinary medicine. HYPOTHESIS: Describe the causes of traumatic and iatrogenic SNI and evaluate which clinical and electrodiagnostic findings predict outcome. ANIMALS: Thirty-eight dogs and 10 cats with confirmed SNI referred for neurologic and electrodiagnostic evaluation. METHODS: Clinical and electrodiagnostic examination results, including electromyography (EMG), motor nerve conduction studies, muscle-evoked potential (MEP), F-waves, sensory nerve conduction studies, and cord dorsum potential (CDP), were retrospectively evaluated. Quality of life (QoL) was assessed based on owner interviews. RESULTS: Surgery (42%) and trauma (33%) were the most common causes of SNI; in dogs, 24% were caused by bites from wild boars. Ability to flex and extend the tarsus was significantly associated with positive outcome in dogs. Mean time from onset of clinical signs until electrodiagnostic evaluation was 67 ± 65 (range, 7-300) days and 65 ± 108 (range, 7-365) days for dogs and cats, respectively. A cut-off amplitude of 1.45 mV for compound motor action potentials (CMAP) was predictive of positive outcome in dogs (P = .01), with sensitivity of 58% and specificity of 100%. CONCLUSIONS AND CLINICAL IMPORTANCE: Clinical motor function predicts recovery better than sensory function. Electrodiagnostic findings also may play a role in predicting the outcome of SNI. Application of the proposed CMAP cut-off amplitude may assist clinicians in shortening the time to reassessment or for earlier suggestion of salvage procedures. Owners perceived a good quality of life (QoL), even in cases of hindlimb amputation.

Presumed septic sacroiliitis in a puppy with unilateral hind limb lameness and sciatic nerve neuropathy.

A 5-month-old female entire Dachshund presented with an acute onset of left hind limb lameness following intense play. There were concurrent intermittent neurological deficits in the left hind limb, and pain in the lumbosacral region and on dorsal flexion of the tail. Computed tomography (CT) imaging revealed an asymmetric widening of the left sacroiliac joint with loss of cortical margins, accompanied by mild osteolytic changes of the adjacent ilium and sacrum highly suggestive of septic sacroiliitis. There was also perilesional steatitis in the region of the sciatic nerve. An 8-week course of antimicrobial therapy was prescribed. Complete resolution of all clinical signs was noted at a 7-month follow up. Sacroiliitis should be considered as a differential for unilateral hind limb lameness with or without intermittent sciatic neuropathy in a puppy in the absence of other orthopaedic conditions.

Risk of iatrogenic damage to the sciatic nerve in dairy cattle.

Sciatic nerve damage in cattle could lead to pain, paralysis and lameness, creating welfare and productivity issues. Damage following intramuscular injection is highlighted in some clinical texts although there is no indication of prevalence. This cross-sectional study investigated the anatomical size and position of the sciatic nerve in four dairy cattle type cadavers. To evaluate the risk of iatrogenic damage, 54 participants placed needles in the dorsal gluteal region of two cadavers each, as per their routine intramuscular injection method. The distance from needle tip to the sciatic nerve was estimated for each. Sixty-nine per cent of injections were placed within 5 cm of the sciatic nerve. Direct nerve puncture occurred in the cadaver in poorest body condition. A short questionnaire revealed that 70 per cent of the participants regularly used the dorsal gluteal region for intramuscular injection and 50 per cent commonly used a volume of ≥20 mL at a single site. It is concluded that the sciatic nerve is at considerable risk of iatrogenic damage. The neck should be promoted as the optimum site for intramuscular injection and improved guidelines are required if the gluteal region is to remain in common use. A lateral site, between the tuber coxae and tuber ischium, is recommended.

Molecular characterization of Marek's disease virus in a poultry layer farm from Colombia.

Marek's disease (MD) is a lymphoproliferative disease caused by an Alphaherpesvirus, genus Mardivirus, serotype 1 (Gallid Herpesvirus 2, GaHV-2) that includes all known pathogenic strains. In addition to Marek's disease virus (MDV) serotype 1, the genus includes 2 distinct nonpathogenic serotypes: serotype 2 (GaHV-3) and serotype 3 (Meleagridis Herpesvirus 1, MeHV-1) which are used in commercially available vaccines against MD. As a result of vaccination, clinical signs are not commonly observed, and new cases are usually associated with emerging variant strains against which the vaccines are less effective. In this study, a commercial layer farm showing clinical signs compatible with MDV infection was evaluated. Histological lesions and positive immunohistochemistry in the sciatic nerve and thymus were compatible with cytolytic phase of MD. GaHV-2, GaHV-3 and MeHV-1 were identified by PCR and qPCR in blood samples from 17 birds with suspected MD. Analysis of the Meq gene of the Colombian GaHV-2 isolate revealed a 99% sequence identity with Asian strains, and in the phylogenetic analysis clustered with vv+ MDV. The analysis of amino acid alignments demonstrated an interruption of the proline rich region in P176A, P217A and P233L positions, which are generally associated with vv+ strains. Some of these changes, such as P233L and L258S positions have not been reported previously. In addition, primary cell cultures inoculated with lymphocytes isolated from the spleen showed typical cytopathic effect of GaHV-2 at 5 d post infection. Based on the molecular analysis, the results from this study indicate the presence of vv+ MDV infection in commercial birds for the first time in Colombia. It is recommended to perform further assays in order to demonstrate the pathotype characteristics in vivo.

Use of physical therapy in a dog with bilateral severe plantigrade stance.

A 3.5 yr old spayed female Staffordshire terrier weighing 25.5 kg was presented with a 7 wk history of bilateral plantigrade stance in the pelvic limbs directly following an ovariohysterectomy procedure. Upon presentation, the dog had bilateral atrophy of the distal pelvic limb muscles, enlarged popliteal lymph nodes, and ulcerative wounds on the dorsa of her rear paws. Orthopedic examination revealed intact calcaneal tendons bilaterally and neurologic examination localized the lesion to the distal sciatic nerve. A diagnosis of compressive and stretch neuropathy was made affecting the distal sciatic nerve branches. Physical therapy modalities included neuromuscular electrical stimulation, ultrasound, and low-level laser therapy. Other therapeutic modalities included the use of orthotics and progressive wound care. The dog had increased muscle mass, return of segmental reflexes, return of nociception, and the ability to walk on pelvic limbs with higher carriage of the hock 15 mo following presentation. The use of custom orthotics greatly increased the quality of life and other physical therapy modalities may have improved the prognosis in this dog with severe bilateral plantigrade stance due to neuropathy.

Post-injection sciatic neuropathy in a cynomolgus macaque (Macaca fascicularis).

BACKGROUND: Intramuscular injection is a common route parenteral used in primates. METHODS: A cynomolgus macaque was evaluated for acute lameness and atrophy of the left leg with no evidence of trauma. RESULTS: History revealed ketamine injection 12 days prior. CONCLUSIONS: Histologic examination supported traumatic injection neuropathy due to intramuscular injection.

Muscle potentials evoked by magnetic stimulation of the sciatic nerve in unilateral sciatic nerve dysfunction.

Magnetic stimulation of the sciatic nerve and subsequent recording of the muscle-evoked potential (MEP) was performed in eight dogs and three cats with unilateral sciatic nerve dysfunction. Localisation of the lesion in the sciatic nerve was based on the history, clinical neurological examination and on results of electromyography examination. Aetiology of the sciatic nerve lesion was diverse. A significant difference was found in MEP between the normal and the affected limbs. In addition, absence of conscious pain sensation, absence of voluntary motor function and a poor outcome seemed associated with the inability to evoke an MEP in the affected limb.

Sciatic neurapraxia as a complication in 1000 consecutive canine total hip replacements.

OBJECTIVES: To report the frequency of sciatic neurapraxia (SN) associated with total hip replacement (THR), to determine outcome (recovery rate) after SN associated with THR, and to identify potential causes of THR-associated SN in dogs. STUDY DESIGN: Prospective study. ANIMALS: Dogs (n=786; 1000 hips) that had THR. METHODS: Logistic regression was used to determine the association with post-THR SN of the variables age, sex, breed, weight, body condition score, severity of presurgical pain, side (right, left), type of prosthesis fixation (cemented, cementless), duration of surgery, surgeon experience (chronologic order), traumatic presurgical luxation, and primary versus revision arthroplasty. RESULTS: The frequency of SN after THR was 19/1000 (1.9%). Two explanatory variables, age at surgery and duration of surgery, were significantly (P<.05) associated with increased probability of SN. Body weight (P=.09), traumatic presurgical luxation (P=.11), and revision versus primary surgery (P=.11) were marginally associated with increased probability of SN. All dogs with SN recovered fully. CONCLUSIONS: SN after THR is not uncommon and complete recovery usually occurs although the recovery time is highly variable. CLINICAL RELEVANCE: Although SN associated with THR typically resolves, surgeons should avoid iatrogenic sciatic nerve injury during THR.

Iatrogenic sciatic nerve injury in eighteen dogs and nine cats (1997-2006).

OBJECTIVE: To report clinical features associated with iatrogenic peripheral nerve injury in dogs and cats admitted (1997-2006) to a referral teaching hospital. STUDY DESIGN: Retrospective study. ANIMALS: Dogs (n=18), 9 cats. METHODS: Patients had acute signs of monoparesis attributable to sciatic nerve dysfunction that developed after treatment. Neurologic examination and electrodiagnostic testing were performed. Surgical therapy was used for nerve entrapment and delayed reconstructive surgery used in other cases. RESULTS: Of 27 nerve injuries, 25 resulted from surgery (18 with treatment of pelvic injuries). Iliosacral luxation repair resulted in tibial (4 cats) and peroneal (3 dogs) nerve dysfunction. Other causes were intramedullary pinning of femoral fractures (3), other orthopedic surgery (cemented hip prosthesis [2] and tibial plateau-leveling osteotomy [1]), and perineal herniorrhaphy [1]. Nerve injury occurred after intramuscular injection (1 cat, 1 dog). Immediate surgical treatment was removal of intramedullary nails, extruded cement, or entrapping suture. Delayed nerve transplantation was performed in 2 dogs. Within 1 year, 13 patients recovered completely, clinical improvement occurred in 7, and there was no improvement in 7. Five of the 7 dogs that did not recover had acetabular or ilium fracture. CONCLUSION: Iatrogenic sciatic nerve injury occurred most commonly during treatment of pelvic orthopedic diseases and had a poor prognosis. Clinical variation in sciatic nerve dysfunction in dogs and cats can be explained by species anatomic differences. CLINICAL RELEVANCE: Iatrogenic sciatic nerve injury leads to severely debilitating locomotor dysfunction with an uncertain prognosis for full-functional recovery.

Early dexamethasone treatment after implantation of a sciatic-nerve cuff decreases the concentration of substance P in the lumbar spinal cord of rats with neuropathic pain.

The main purpose of this study was to evaluate the effects of early dexamethasone treatment on pain-related peptides at an early stage in the development of neuropathic pain induced by implantation of a sciatic nerve cuff in Sprague Dawley rats (body weight 250 to 350 g). The rats were tested for touch sensitivity with the use of von Frey filaments before and 3 d after cuff implantation (n = 12) or sham surgery (n = 6). Half of the cuff-implanted rats received dexamethasone, 1 mg/kg intraperitoneally, 1 h after surgery. Spinal cords were collected on the 3rd day after surgery, and the lumbar enlargement was processed for the detection of selected peptides (neurotensin, substance P, cholecystokinin [CCK], vasoactive intestinal peptide, and calcitonin gene-related peptide) by means of liquid chromatography and tandem mass spectrometry. The right sciatic nerve of each rat was collected, fixed, and stained for histopathological evaluation. Except for neurotensin, all the peptides showed an increased concentration with neuropathic pain; however, the differences were significant (P < 0.05) only for substance P and CCK. In the animals treated with dexamethasone, mechanical allodynia was less pronounced (P < 0.01), and only the concentration of substance P was decreased significantly (P < 0.05). Sciatic nerve sections showed a decrease in C (P < 0.01) and Adelta (P < 0.03) fibres with neuropathic pain and a nearly normal percentage of C fibres after dexamethasone treatment. The dexamethasone-treated animals also had less inflammation detectable microscopically at the nerve constriction site compared with cuff-implanted animals that were not treated with dexamethasone. Our results suggest that in the early stages of neuropathic pain induced by an inflammatory process, dexamethasone may be a useful treatment and that substance P plays an important role in pain perception.

Use of an ankle-foot orthosis in a dog with traumatic sciatic neuropathy.

Traumatic unilateral sciatic neuropathy secondary to a gunshot wound was diagnosed in a seven-month-old, intact male golden retriever. Findings on neurological assessment, performed after cardiovascular stabilisation, were incompatible with a return to normal limb function. An ankle-foot orthosis was used to correct excessive flexion of the digits and tarsus. This device greatly improved the dog's willingness to ambulate and could serve as an alternative to amputation in companion animals with severe sciatic axonotmesis or neurotmesis. Complications associated with chronic tibiotarsal hyperflexion necessitated a pantarsal arthrodesis one year after initial presentation; the dog also developed cranial cruciate disease in the affected limb three years after the gunshot injury.

A comparison of sciatic nerve neuropathy in diabetic and aged rats.

We compared the development of sciatic nerve neuropathy in young diabetic rats with that in non-diabetic aged rats. Diabetes was induced in six-month old rats by injection with alloxan and was moderately controlled by single daily injections of insulin. Blood insulin levels in diabetic rats were significantly reduced compared to the aged animals, and glucose was significantly higher in diabetic rats. Sciatic nerve conduction velocities were measured monthly. Both motor and sensory conduction velocities decreased in the diabetic rats to a level that was similar to those in 36-month old rats. The decreases in conduction velocities in the diabetic rats were most dramatic during months 6 through 12 of diabetes. After 6 and 12 months of diabetes, sciatic nerves were examined by electron microscopy and compared to nerves from 24- and 36-month old rats respectively. Ultrastructural changes in the sciatic nerves of diabetic rats at 6 months included disruptions of myelin and dense axoplasm. In comparison, the 24-month old rats only had distorted contours of the nerve fibres. After 12 months of diabetes, the axoplasm had large spaces and the myelin was thickened and deformed. The axoplasm of 36-month old rats was normal in appearance; however the myelin sheath was thickened and split into layers. The Schwann cells were vacuolated and irregular in shape. These observations indicate that diabetes results in the early onset of age-like changes in the sciatic nerve. It suggests that the control of hyperglycemia in humans may preserve sciatic nerve structure and function.

Resistance to Marek's disease herpesvirus-induced lymphoma is multiphasic and dependent on host genotype.

Genotype-dependent differences in Marek's disease (MD) susceptibility were identified using 14-day-old line N and 6(1) (resistant) and 151 and 7(2) (susceptible) inbred chickens infected with HPRS-16 MD virus (MDV). All line 72 chickens developed progressive MD. Line 15I had fluctuating MD-specific clinical signs and individuals recovered. A novel histologic scoring system enabled indices to be calculated for lymphocyte infiltration into nonlymphoid organs. All genotypes had increased mean lesion scores (MLSs) and mean total lesion scores after MDV infection. These differed quantitatively and qualitatively between the genotypes. Lines 6(1) and 7(2) had a similar MLS distribution in the cytolytic phase, although scores were greater in line 7(2). At the time lymphomas were visible in line 7(2), histologic lesions in line 6(1) were regressing. AV37+ cells were present in similar numbers in all genotypes in the cytolytic phase, suggesting that neoplastically transformed cells were present in all genotypes regardless of MD susceptibility. After the cytolytic phase, AV37+ cell numbers increased in lines 7(2) and 15I but decreased in lines 6(1) and N. In the cytolytic and latent phases, in all genotypes, most infiltrating cells were CD4+. After this time, line 7(2) and 15I lesions increased in size and most cells were CD4+; line 6(1) and N lesions decreased in size and most cells were CD8+. In all genotypes, AV37 immunostaining was weak in lesions with many CD8+ cells, suggesting that AV37 antigen expression or AV37+ cells were controlled by CD8+ cells. The rank order, determined by clinical signs and pathology, for MD susceptibility (highest to lowest) was 7(2) > 15I > 6(1) > N.