Strain differences in the branching of the sciatic nerve in rats

The sciatic nerve in the rat is the site most often used for peripheral nerve regeneration studies. The length of sciatic nerve available for research, however, depends on the point at which the sciatic nerve divides into the peroneal and tibial nerves. In the present study, the hind limbs of 150 adult male rats of five different strains (Sprague-Dawley, Fischer 344, Wistar-Han, Lewis and Nude) were analysed with regard to femur length, the point at which the sciatic nerve divides into the tibial and peroneal nerves, and where these are surrounded by the same epineurium, and the point at which they are encased in individual epineurial sheaths. The results indicate that the lengths of sciatic nerve are fairly constant in all strains of rats. In absolute terms, they amount to about one-third of the length of the femur for stretches of undivided sciatic nerve, and up to nearly half of the femur length for stretches where the tibial and peroneal nerves are already present, but are still enclosed by the same epineurium. In 61.7% of the hind limbs examined in Fischer rats, however, no sciatic nerve could be seen as such, but only in the form of its successors surrounded by the separate epineuria. This makes it highly advisable not to use male adult Fischer rats in peripheral nerve regeneration studies with the sciatic nerve as the point of focus.     

ULTRASONOGRAPHIC ASSESSMENT OF THE CANINE SCIATIC NERVE

To describe the ultrasonographic technique for investigation of the canine sciatic nerve, four canine cadaver pelvic limbs, two live healthy dogs, and five canine patients with suspected peripheral sciatic nerve lesions were examined with a high-resolution linear ultrasound transducer. The caudal part of the lumbosacral trunk and the origin of the sciatic nerve were visualized through the greater ischiatic foramen. The two components of the sciatic nerve, common peroneal and tibial nerves, were distinguished along the entire length of the nerve, until they branched at the level of the distal femur. In healthy live dogs they appeared as two adjacent hypoechoic tubular structures with internal echotexture of discontinuous hyperechoic bands, surrounded by a thin rim of highly echogenic tissue. The common peroneal component had a smaller diameter and was on the cranial aspect of the tibial component. An ultrasonographic lesion compatible with a peripheral nerve sheath tumor was found in one dog. Improved understanding of the ultrasonographic anatomy of the sciatic nerve supports clinical use of this modality.     

Electrical stimulation of lumbar spinal nerve roots in dogs

The aim of this study was to test the applicability of electrical stimulation of lumbar spinal nerve roots and obtain normative electrical root stimulation (ERS) data for L7 nerve root and sciatic nerve in dogs. For that purpose ERS and sciatic nerve stimulations were performed consecutively, in totally 40 healthy dogs. ERS was applied in the L7/S1 intervertebral space via monopolar needle electrodes. Muscle responses were recorded from the gastrocnemius muscles on the left and right hind limbs. Sciatic nerve stimulation was performed at the greater trochanter level on the left hind limb, with records obtained from the left gastrocnemius muscle. Mean root latencies of the left and right side were 5.22?±?0.49 ms and 5.29?±?0.53 ms, respectively. There was no significant difference in root latency between the right and left sides. The mean terminal latency was 3.82?±?0.46 ms. The proximal motor nerve conduction velocity of the sciatic nerve was 63.15?±?3.43 m/s. The results of this study show that ERS provides objective data about the integrity of lumbar spinal nerve roots by evaluating the entire population of motor fibres and total length of the motor axon in dogs. ERS can be considered a useful diagnostic method for confirmation of diagnoses of lumbosacral diseases.     

ULTRASONOGRAPHY OF PERIPHERAL NERVES DURING WALLERIAN DEGENERATION AND REGENERATION FOLLOWING TRANSECTION

Ultrasonography was performed on sciatic, tibial and/or peroneal nerves and interosseous muscles in 7 dogs using a ultrasound machine with a 7.5 MHz linear array transducer. A tibial nerve was transected near the distal aspect of the bellies of the gastroenemius muscle. Serial neurologic examinations, electromyography, and ultrasonography were performed before and after surgery. Dogs were euthanized at variable intervals and histopathology performed on nerve samples. In sagittal images, normal nerves had hyperechoic walls with multiple internal linear echoes. In transverse images, the nerves were round or oval hyperechoic structures with internal punctate echoes. After transection, the proximal stump was consistently seen whereas the distal stump and nerve were harder to identify. Neuromas were present in all 5 dogs followed beyond 2 days and appeared as hypoechoic bulbous swellings most apparent at 3 weeks after surgery. Only 1 dog developed a neuroma large enough to be considered of potential clinical significance. Four dogs were followed beyond 2 months. Regeneration was evidenced by a steady growth of nerve with an irregular outline (2 dogs) or by a knobby connection between the proximal and distal stumps (1 dog). Regeneration was not detected in 1 dog.     

Electrophysiologic studies of the cutaneous innervation of the pelvic limb of male dogs

The area of skin supplied by the afferent fibers in one cutaneous nerve is called the cutaneous area (CA) for that nerve. The CA of peripheral branches of lumbar and sacral spinal nerves responsive to the stimulation of hair follicle mechanoreceptors were mapped in 27 dogs. The amount of overlap among the CA was similar to that found for other CA of the body. The CA of peripheral branches of the sciatic nerve were restricted to the lateral, cranial, and caudal aspects of the pelvic limb distal to the stifle. The CA of the saphenous nerve was located on the medial side of the limb, except for a small area located on the lateral side of the crus. The distal part of the CA of the saphenous nerve was completely overlapped in the hind paw by branches of the superficial peroneal nerve laterally and the medial plantar branch of the tibial nerve medially. The CA for the deep peroneal nerve was located on the dorsal surface of the webbing between digits 2 and 3 and the adjacent skin of these digits. The CA of the plantar branches of the tibial nerve were small in comparison with the diameter of the nerve, suggesting that these branches contained nerve fibers supplying other, deeper structures in the hindpaw and that damage to these nerves would interfere with cutaneous sensation in only a small region on the plantar surface of the hindpaw. Knowledge of the CA of the various branches of the sciatic nerve allows more accurate localization of injury to the sciatic nerve or its branches by using areas of anesthesia.     

Open reduction and internal fixation with a locking plate for the treatment of a femoral fracture in a ferret (Mustela putorius furo)

Long bone fractures in ferrets (Mustela putorius furo) are usually traumatic in etiology, and the femur is commonly affected [1]. A 4-year-old, castrated male ferret was examined for acute, non-weight-bearing lameness of the left pelvic limb after presumably falling from its elevated enclosure. Clinical and radiographic evaluation showed a complete, comminuted fracture of the proximal diaphyseal third of the left femur. Open reduction and internal fixation (ORIF) of the left femoral fracture was performed with cerclage wires and a 1.5 mm locking compression plate with associated locking screws. Anatomic reconstruction was achieved, and postoperative radiographs confirmed appropriate fracture fragment apposition, limb alignment, and implant placement. At 9 weeks postoperatively, the ferret was ambulatory with no evidence of lameness, and complete radiographic union was noted. This is the first published report of the use of a bone plate for femoral fracture stabilization in a ferret. Bone plates, including locking plates, could be considered for long bone fracture stabilization in ferrets as an alternative to other methods.     

Treatment of a femoral fracture with a titanium locking compression plate distal femur (LCP‐DF) in a young donkey

A closed complete mid‐diaphyseal spiral fracture of the left femur in a one‐year‐old donkey was treated with a 4.5 mm titanium locking compression plate distal femur (LCP‐DF)¹. This plate was originally manufactured for human orthopaedics, primarily for femoral osteosynthesis. The LCP‐DF¹ has a distal head plate that was advantageous in this case because the distal fragment was smaller. Post operative radiographs showed optimal femoral reconstruction and a callus was present 3 weeks after surgery. The donkey was sound at the walk and trot 2 months after surgery. Radiographs taken 5 months after surgery showed stable implants and complete healing without complications.     

Cutaneous saphenous nerve graft for the treatment of sciatic neurotmesis in a dog

CASE DESCRIPTION: A 2-year-old Griffon Vendéen was examined because of a 1-month history of right hind limb lameness after a traumatic injury. CLINICAL FINDINGS: Neurologic examination revealed monoplegia and anesthesia of the right hind limb distal to the stifle (femorotibial) joint except for the area supplied by the cutaneous saphenous nerve. Results of electromyographic testing were consistent with a severe lesion of the tibial and peroneal nerves at the level of the stifle joint. TREATMENT AND OUTCOME: Exploratory surgery revealed an 80-mm-long gap in both the peroneal and tibial branches of the right sciatic nerve. A section of the left cutaneous saphenous nerve was interposed to graft the nerve defects. The dog received joint mechanotherapy and electrophysiologic therapy during the reinnervation process. Ten months after surgery, the dog had recovered almost completely. Neurologic examination revealed diminished flexion of the tarsal and digital joints. Repeat electromyographic testing revealed no abnormal spontaneous electrical activity in the right hind limb musculature, and small compound muscle action potentials were recorded in the right interosseous and cranial tibial muscles. CLINICAL RELEVANCE: Without surgical treatment, neurotmesis injury results in poor recovery of motor and sensory functions and may result in amputation. If a nerve defect exists, nerve grafting should be considered, even if the procedure is delayed until well after the injury. The sensory portion of the cutaneous saphenous nerve is a potential source of peripheral nerve for grafting in dogs. Reinnervation is a long-term process and physiologic support and owner involvement are necessary, but nearly complete functional recovery is possible.     

Multiple myeloma with central nervous system involvement in a cat

CASE DESCRIPTION: A 1.5-year-old spayed female domestic shorthair cat was admitted for hind limb locomotor difficulties and signs of pain along the lumbar portion of the vertebral column. At the time of referral, the cat was paraparetic with deficits in the spinal reflexes of the hind limbs. Neuroanatomic localization was at the L6-S2 spinal cord segments, corresponding approximately to the region of the L4-L6 vertebral bodies. CLINICAL FINDINGS: Radiography revealed a mixed osteolytic-proliferative lesion within the body of L5 involving the cranial end plate, as well as punctate radiolucencies in the distal portion of the femur. Magnetic resonance imaging revealed an intramedullary spinal cord lesion along with extensive meningeal and nerve root lesions in the area of the L4-L6 vertebral bodies. Cytologic analysis of a bone marrow aspirate from the right trochanteric fossa revealed a substantial plasma cell infiltrate. Analysis of CSF revealed a high protein concentration and morphologically abnormal plasma cells. Urine, but not serum, protein electrophoresis revealed a sharp gamma-globulin peak consistent with a monoclonal band of Bence-Jones proteins. The diagnosis was multiple myeloma. TREATMENT AND OUTCOME: The cat was treated with melphalan and prednisolone. A rapid clinical response was reported, and by week 3 after diagnosis, the cat's locomotion and behavior had normalized. However, by month 4, multifocal neurologic deficits were evident. The cat was euthanized at 9 months because of tetraparesis and substantial weight loss. CLINICAL RELEVANCE: To our knowledge, this is the first report of myeloma in a cat that had electrophoretically detectable light chain proteinuria but lacked a detectable serum monoclonal gammopathy.     

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.     

Distribution of a lidocaine-methylene blue solution staining in brachial plexus, lumbar plexus and sciatic nerve blocks in the dog

ObjectiveTo determine the influence on the distribution of the volume of a local anaesthetic-methylene blue solution at three different nerve block sites in the dog.Study designRandomized, controlled, blinded experimental trial.Animals23 hound-cross dogs weighing 16–40 kg and aged 2 ± 0 years (mean ± SD).MethodsDogs were anaesthetized and randomly assigned to three groups of seven or eight dogs each, based on volume administered: low, medium and high volume (L, M and H). Using electrolocation, the injection was performed after a positive response was elicited (flexion of the elbow for the brachial plexus block, quadriceps contractions for the lumbar plexus and dorsiflexion/plantar extension of the foot for the sciatic nerve block). At the brachial plexus site, groups L, M and H received 0.075, 0.15 and 0.3 mL kg⁻¹, respectively. At the lumbar plexus site, groups L, M and H received 0.1, 0.2 and 0.4 mL kg⁻¹, respectively. At the proximal sciatic nerve site, groups L, M and H received 0.05, 0.1 and 0.25 mL kg⁻¹, respectively. Necropsies were performed immediately following euthanasia. Staining of ≥2 cm along the nerve was considered sufficient; the proportions sufficient were compared with Fisher's exact test. The volume was recommended when all the relevant nerves were stained sufficiently in all or all but one of the dogs within the group.ResultsIn the brachial plexus, only in group H were all the nerves stained sufficiently. In the lumbar plexus site, no statistical difference was found, but we suggest the H group volume to balance sufficient and excessive staining. At the sciatic nerve site, all volumes tested produced sufficient staining in all (or all but one) dogs.Conclusions and clinical relevanceVolumes of 0.3 and 0.05 mL kg⁻¹ produced sufficient distribution for performing brachial plexus, and sciatic nerve blocks, respectively. Additionally, a volume of 0.4 mL kg⁻¹ might also be adequate for a lumbar plexus block (no statistical significance was reached).     

N. femoralis, N. obturatorius and N. ischiadicus: deviation in creation in the dogs

Two hundred and twelve dog cadavers belonging to different breeds were examined, to investigate the formation of the femoral, obturator and the sciatic nerve. Besides the commonly described formation patterns of the mentioned nerves, some variations were also found. These variations were not gender-related, but on the other hand we discovered a certain correlation between the variations appearing in the formation of the femoral, obturator and the sciatic nerve. In 74.05% of cases, the femoral nerve was formed from ventral branches of the 4th, 5th and 6th lumbar nerve, and 16.98% of the dogs had the nerve formed from ventral branches of the 3rd, 4th and 5th lumbar nerve. Many dogs (i.e. 2.30%) had the femoral nerve formed from the ventral branches of the 5th, 6th and 7th, the 3rd, 4th, 5th and 6th or the 4th, 5th, 6th and 7th lumbar nerve, respectively. In 1.88% of dogs in particular, the femoral nerve was formed from ventral rami of the 4th and 5th lumbar nerve. In 66.98% of the examined dogs, the obturator nerve was formed from the ventral branches of the 4th, 5th and 6th lumbar nerve, followed by 16.59% of the dogs with the obturator nerve formed from the ventral rami of the 4th and 5th lumbar nerve and 9.43% of dogs in which the nerve was formed from the ventral branches of the 5th and 6th lumbar nerve. In 4.71% of dogs, the obturator nerve was formed from the ventral rami of the 4th, 5th, 6th and 7th lumbar nerve, while only 2.30% of the examined dogs had the same nerve formed from the ventral branches of the 5th, 6th and 7th lumbar nerve. The sciatic nerve was formed from ventral branches of the 6th and 7th lumbar nerve and the 1st sacral nerve in 86.79% of the dogs. In 5.18% of cases, the same nerve was formed from a junction of the ventral branches of the 7th lumbar and the 1st and 2nd sacral nerve, and, in the same percentage of cases, it was formed from a junction of ventral branches of the 6th and 7th lumbar nerve and the 1st and 2nd sacral nerve. In 2.83% of the dogs, it was formed from a junction of the ventral branches of the 6th and 7th lumbar and the 1st sacral nerve. The correlation of variations established in the formation of the femoral, obturator and the sciatic nerve was not statistically significant.     

Extradural spinal liposarcoma in a dog.

An 8-year-old female Doberman Pinscher was examined because of progressive, asymmetric, ambulatory caudal paraparesis. Myelography revealed extradural left ventrolateral spinal cord compression over the first and second lumbar vertebral bodies. A left hemilaminectomy, extending from the thirteenth thoracic to the second lumbar vertebrae, was done, and an extradural mass was removed. The tumor was identified histologically as myxoid liposarcoma. The dog's neurologic function improved gradually after surgery; however, at 7 months after surgery, hind limb neurologic function deteriorated rapidly over a 5-week period, presumably because of local recurrence of the tumor. The dog was euthanatized; necropsy was not permitted.     

ULTRASONOGRAPHY OF PERIPHERAL NERVES IN THE NORMAL ADULT HORSE

A study of the ultrasonographic appearance and size of the sciatic, tibial, peroneal, suprascapular, radial, median, and ulnar nerves and a comparison with the anatomic size and location of these nerves in the normal adult horse is reported. Cadavers and live horses were studied. Landmarks for localization and techniques for nerve identification are described. The depth and diameter of each nerve at various locations and the success rate in imaging each nerve are reported. Statistically significant correlations were found between anatomically and ultrasonographically measured nerve depths and diameters. The success rate in identifying nerves was 70% in the live horses and 49% in cadavers, with the deep peroneal nerve being the easiest to identify. Some applications of this technique in horses are discussed.     

Ventricular pneumocephalus and septic meningoencephalitis secondary to dorsal rhinotomy and nasal polypectomy in a dog

CASE DESCRIPTION: A 4-year-old sexually intact female French Bulldog was evaluated because of lethargy, anorexia, and chronic rhinitis-sinusitis. The dog had nasal discharge of 18 months' duration; dorsal rhinotomies were performed 3 months and 2 weeks prior to referral. CLINICAL FINDINGS: On initial evaluation, intraventricular pneumocephalus and sinusitis were diagnosed; CSF analysis revealed high total protein concentration and mononuclear pleocytosis. The dog's condition improved with treatment. Two weeks after discharge, it was treated by a local veterinarian because of upper airway obstruction; 3 days later, the dog was referred because of seizures. Computed tomography revealed a large fluid-filled, left lateral ventricle and a soft tissue mass protruding through a cribriform plate defect. The mass was histologically consistent with brain tissue. Findings of clinicopathologic analyses were unremarkable. Results of cytologic examination of a CSF sample were indicative of septic, suppurative inflammation, and bacteriologic culture of CSF yielded Escherichia coli. TREATMENT AND OUTCOME: Amputation of the herniated olfactory bulb and antimicrobial treatment resolved the septic meningoencephalitis, but neurologic deficits recurred 6 weeks later. Definitive correction of the cribriform plate defect with bone and fascial grafts was attempted. Postoperative rotation of the bone graft resulted in cerebral laceration and hemorrhage, and the dog was euthanized. CLINICAL RELEVANCE: Findings suggest that following dorsal rhinotomy and nasal polypectomy surgery, the dog developed herniation of the left olfactory bulb, intra-ventricular pneumocephalus, and septic meningo-encephalitis because of a cribriform plate defect. Care must be taken to prevent rotation of bone grafts used in cribriform defect repair.     

Mycobacterial neuritis in a cat

A 2-year-old spayed female domestic shorthair cat was referred for evaluation of rapidly progressive lameness of the right hind limb, which was paralyzed. Histologic examination of biopsy specimens revealed pyogranulomatous inflammation affecting the sciatic, common peroneal, and tibial nerves, and slender, beaded, acid-fast bacilli within macrophages, nerve fibers, and degenerate axons. A diagnosis of mycobacterial neuritis was made and the cat was treated with clofazimine and enrofloxacin for extended periods. Treatment was partially effective; the goal of returning normal function to the limb was not achieved, but disease progression was halted and the cat remained a viable pet.     

Toxic peripheral neuropathy with demyelination in Sprague-Dawley rats given CGS 21595--a 5-lipoxygenase inhibitor.

Male and female Sprague-Dawley rats were given CGS 21595, a pro-drug that is almost immediately metabolized to CGS 19213, a naphthoquinone that acts as a 5-lipoxygenase inhibitor. The compound was administered by gavage to five groups of Sprague-Dawley rats (group Nos. 1, 5, n = 30; group Nos. 2-4, n = 20) at daily doses of 0, 50, 150, 500, or 1,000 mg/kg for 13 weeks. Rats in the higher dose groups had a reduced weight gain, but significant neurologic signs were not observed. A peripheral neuropathy consisting predominantly of myelin destruction in the spinal nerve roots and sciatic nerves in male rats treated with greater than or equal to 150 mg/kg CGS 21595 and in female rats treated with greater than or equal to 50 mg/kg CGS 21595 for 13 weeks. This lesion was not fully reversible after a recovery period of 4 weeks. Lesions consisted of ballooning of myelin sheaths, infiltration by macrophages, demyelination, and occasional areas of remyelination. Axons were generally preserved, and the brain and spinal cord were not affected. Male and female rats in all treatment groups had cytoplasmic hyaline droplets in the proximal renal tubules. This change was reversible after 4 weeks and was not associated with any other adverse effects on the kidney.     

Contrast-enhanced ultrasonography for evaluation of the blood perfusion of sciatic nerves in healthy dogs

Blood supply to the peripheral nerves is essential for fulfilling their structural and functional requirements. This prospective, experimental, exploratory study aimed to assess the feasibility of contrast-enhanced ultrasonography (CEUS) for evaluating blood perfusion of the sciatic nerve in normal dogs. Contrast-enhanced ultrasonography examinations were performed on the bilateral sciatic nerves after bolus injection of Sonazoid™ (0.015 mL/kg) in 12 healthy Beagles for 150 s. Then, qualitative assessment of the wash-in timing, degree and enhancement patterns, and quantitative measurement of the peak intensity and time to peak intensity were performed from the sciatic nerve. The results were compared to those obtained from the adductor muscle around the nerve and caudal gluteal artery. After contrast agent injection, the sciatic nerve was enhanced at approximately 13–14 s, immediately after wash-in of the caudal gluteal artery. The peak intensity of the sciatic nerve was significantly lower than that of the caudal gluteal artery and higher than that of the adductor muscle. The time to peak intensity was significantly slower than that of the caudal gluteal artery; but was not significantly different from that of the adductor muscle. There were no significant differences in the peak intensity and time to peak intensity between the left and right sciatic nerves. These results demonstrate the feasibility of CEUS to assess blood perfusion of the sciatic nerve in healthy dogs qualitatively and quantitatively. This result from healthy dogs could serve as a reference for further studies that evaluate the sciatic nerve under pathological conditions.     

Unilateral limb enlargement in a dog with a malignant peripheral nerve sheath tumor

A 3- to 4-month-old female Golden Retriever dog presented with right hind limb enlargement. Physical examination of the limb and radiographic findings initially included soft tissue swelling with elongation, bowing, and cortical irregularity of the femur and tibia. During a period of approximately 7 months, pathology in the limb progressed to include tarsal laxity, muscle atrophy, avulsion of the gastrocnemius muscle, and luxation of the patella. During surgical intervention to shorten the limb and repair the patellar luxation, a large soft tissue cyst was identified along the caudal aspect of the femur and stifle. The limb was later amputated, and a final diagnosis of malignant peripheral nerve sheath (PNS) tumor of the sciatic nerve and surrounding soft tissues was made. The unilateral limb enlargement in this dog appears to have been because of the development and progression of a malignant PNS tumor. The presentation and associated pathologic changes in the limb are unusual for canine PNS tumor but have similarities with neurofibromatosis in the limbs of humans.