Electrodiagnostic testing in dogs with disorders of the spinal cord or cauda equina.

Electrodiagnostic (EDX) testing is uncommonly utilized in dogs other than for investigation of disorders of the neuromuscular system. In dogs with diseases affecting the spinal cord or cauda equina, EDX testing can provide functional data complementary to imaging information that together can guide therapeutic and management approaches. Additionally, in some clinical scenarios, EDX testing prior to advanced imaging is integral to identifying if there is spinal cord or cauda equina involvement and can aid in determining the appropriate diagnostic path. This review will outline EDX testing methods that have been reported in dogs relating to the diagnosis, monitoring or prognosis of various conditions affecting the spinal cord and cauda equina. The various tests will be briefly outlined regarding how they are performed and what information is provided. The main focus will be on clinical applications including highlighting situations where EDX testing is useful for differentiating between neurologic and non-neurologic presentations. Additional ways these EDX techniques could be incorporated in the management of diseases of the spinal cord and cauda equina in dogs will be presented.

Mineralization of the transverse ligament of the atlas causing compressive radiculopathy. Resolution following odontoidectomy and atlantoaxial arthrodesis.

OBJECTIVE: To describe a case of a Boxer dog with radiculopathy due to mineralization of the transverse ligament of the atlas and subsequent resorption and resolution of clinical signs after atlantoaxial arthrodesis and odontoidectomy. CASE REPORT: A five-year-old neutered female Boxer dog was presented with a four-month history of cervical hyperaesthesia refractory to medical management. Neurological examination and magnetic resonance imaging indicated a diagnosis of radiculopathy due to cervical nerve root impingement by dystrophic mineralization of the transverse ligament of the atlas. Odontoidectomy was performed by a ventral approach and atlantoaxial arthrodesis was achieved with a ventral composite polymethylmethacrylate and pin fixation. RESULTS: Atlantoaxial arthrodesis and progressive resorption of the mineralization following stabilization facilitated indirect decompression. The radioclinical diagnosis and response to arthrodesis was considered analogous to retro-odontoid pannus in the human. CLINICAL RELEVANCE: A clinical condition similar to retro-odontoid pannus may exist in the canine and may be amenable to atlantoaxial arthrodesis.

Femoral nerve entrapment in a dog with diffuse idiopathic skeletal hyperostosis.

OBJECTIVE: To report femoral neuropathy caused by nerve entrapment associated with diffuse idiopathic skeletal hyperostosis (DISH). STUDY DESIGN: Case report. ANIMAL: Seven-year-old female spayed Boxer dog. RESULTS: Entrapment of the right femoral nerve due to DISH caused a femoral nerve deficit and atrophy of muscle groups associated with the affected nerve. A combination of computed tomography and magnetic resonance imaging was performed to provide a diagnosis. Amputation of the right transverse process of the sixth lumbar vertebra at the level of nerve entrapment relieved the neurological abnormality. CONCLUSIONS: Nerve entrapment leading to neurapraxia may occur concurrently with DISH and surgery in this case was successful in restoring function. CLINICAL RELEVANCE: Peripheral neuropathy from nerve entrapment should be considered in patients with DISH. Surgical amputation of impinging osseous structures may be indicated for relief of femoral neuropathy.

Magnetic resonance imaging of suspected idiopathic bilateral C2 hypertrophic ganglioneuritis in dogs.

OBJECTIVES: To report the magnetic resonance imaging and clinical features of suspected idiopathic bilaterally symmetric hypertrophic ganglioneuritis affecting the C2 nerve roots. METHODS: Retrospective analysis of case records of dogs with imaging findings suggestive of idiopathic bilateral C2 neuritis. Data analysed included signalment, history, clinical signs, clinical pathology results and magnetic resonance imaging findings. Nerve root enlargement and spinal cord changes were classified as clinically significant or incidental, and further graded as mild, moderate or severe based on the degree of spinal cord distortion/compression. Imaging features were also correlated with severity of neurological deficits. RESULTS: Twelve dogs, including nine Staffordshire bull terriers showed magnetic resonance imaging features suggestive of idiopathic hypertrophic neuritis of C2 nerve roots. Findings were considered incidental (4/12) or clinically significant (8/12) based on prior neurological examination. Changes were best visualised on transverse images at the level of the C1-2 intervertebral foramina. The degree of associated spinal cord compression subjectively correlated with the severity of the neurological deficits. All cases with clinically significant lesions that were treated with corticosteroids responded favourably. CLINICAL SIGNIFICANCE: Bilaterally symmetric C2 neuritis likely represents idiopathic hypertrophic ganglioneuritis. Staffordshire bull terriers appear over represented. Immunosuppressive doses of corticosteroids should be considered for clinically significant lesions.

Priapism associated with lumbar stenosis in a dog.

Priapism, a persistent long-lasting involuntary erection of the penis, is uncommon in dogs. In this report, the case of a 13-year-old male Pointer, referred to our services due to persistent exposition of the penis, is described. This condition was consecutive to an intermittent priapism situation lasting for several days, which has been initially attributed to the inflammation and haematoma associated with a perianal bite. The owners became unable to retract the penis into the prepuce. At presentation, the dog was anorectic for 48 h, intolerant to manipulation, and showed poor body condition and unsteady locomotion. During physical evaluation, a marked engorgement of the local vessels in the prepuce and penis was found. An abdominal X-ray was asked under the suspicion of a neurogenic origin for the clinical situation, which showed evidences of spondylosis. After discussion of the clinical condition, the owners asked for euthanasia. The necropsy confirmed the engorgement of the regional vessels deriving from the pudendal arteries and blood accumulation within all the cavernous spaces, accompanied by congestion and thrombosis within the erectile structures of the penis. No significant changes were observed in the pelvic organs that could be at the origin of priapism. The lumbar-sacral spinal regions were carefully inspected and evidenced signs of L7-S1 stenosis due to spondylosis. The case presented herein is a rare situation of priapism of neurogenic origin in a dog. Necropsy findings suggest that it was consecutive to cauda equina compression due to lumbar spinal stenosis.

Caudal compression of the infraorbital nerve: a novel surgical technique for treatment of idiopathic headshaking and assessment of its efficacy in 24 horses.

UNLABELLED: REASONS FOR DESIGNING AND REPORTING TECHNIQUE: Idiopathic headshaking has remarkable similarities to human neuropathic facial pain syndromes associated with post herpetic and trigeminal neuralgia. These derive from abnormal sensory function within the peripheral or central pathways of the trigeminal nerve (TgN). Limiting input from the TgN can be helpful in controlling the perception of pain. Rhizotomy of the infraorbital branch of the TgN as it emerges from the infraorbital canal has been reported but has a poor efficacy. A novel technique involves compression of the nerve at a more caudal location within the infraorbital canal and the technique requires validation. HYPOTHESIS: Caudal compression of the infraorbital nerve with platinum coils, performed in horses diagnosed with idiopathic headshaking, results in a decrease in clinical signs. METHODS: Caudal compression of the infraorbital nerve, using platinum embolisation coils, was performed under fluoroscopic guidance. Clinical records of 24 idiopathic headshakers that had undergone this procedure were reviewed. Follow-up information was obtained by telephone questionnaire with the owner or referring veterinary surgeon. RESULTS: All 24 horses had at least one surgical procedure. Median follow-up time was 6 months. There were 2 horses which had surgery 2 weeks before follow-up and these were excluded from the analysis of outcome. Following one surgery, 13/22 horses (59.0%) had a successful outcome. Of the 9 horses that did not improve, surgery was repeated in 6 cases. Two of these horses had a successful outcome. Overall, a successful outcome was obtained in 16/19 horses (84.2%). CONCLUSIONS: This surgical technique is likely to prevent input from the TgN at a more caudal location then the previously described infraorbital neurectomy. The technique requires refinement.

Compressive damage to the deep branch of the lateral plantar nerve associated with lameness caused by proximal suspensory desmitis.

OBJECTIVE: To describe pathologic changes in the deep branch of the lateral plantar nerve (DBLPN) of horses determined to be lame because of proximal suspensory desmitis (PSD), and to report the outcome after treatment by excision of a segment of the horses' DBLPN. STUDY DESIGN: Retrospective case series. ANIMALS: Adult horses (n=16). METHODS: Horses determined to be lame on one or both pelvic limbs because of PSD were treated by excision of a segment of the DBLPN, and 30 nerves were examined histologically. Owners were contacted to obtain information about the horses >or=6 months after surgery. RESULTS: Histologic changes suggestive of chronic nerve compression were identified in both nerves of 11 bilaterally lame horses and in the lame limb of 5 unilaterally lame horses. The nerve of the sound limb of 2 of 3 unilaterally lame horses that had bilateral nerve resection also had histologic changes compatible with nerve compression. Ten of 16 horses (62.5%) with follow-up information returned to soundness after excision of the DBLPN. CONCLUSIONS: Pathologic changes of the DBLPN associated with compression may complicate PSD of the pelvic limbs. Excision of the nerve may resolve lameness caused by PSD. CLINICAL RELEVANCE: Horses lame because of PSD of the pelvic limb may remain lame after desmitis has resolved because of compression of the DBLPN. Excising a portion of this nerve may resolve lameness.

Chiari-like malformation with syringomyelia in the Cavalier King Charles spaniel: long-term outcome after surgical management.

OBJECTIVE: To evaluate long-term success of cranial cervical decompression for management of canine Chiari-like malformation with syringomyelia (CM/SM). STUDY DESIGN: Retrospective clinical study. ANIMALS: Cavalier King Charles spaniels (n=15). METHODS: After diagnosis by magnetic resonance imaging (MRI) dogs had cranial cervical decompression with durotomy. Seven dogs had the durotomy patched with biocompatible collagen matrix. Clinical outcome was monitored for >12 months. RESULTS: All dogs either improved (80%) or were unchanged (20%) postoperatively. Postoperative MRI in 6 dogs revealed persistence of syringomyelia. Seven dogs (47%) subsequently deteriorated, 0.2-2.3 years after surgery (mean, 1.3 years) and 2 dogs were eventually euthanatized as a consequence. Twelve dogs were still alive, 1-6.5 years after surgery (mean, 2.5 years). CONCLUSION: Cranial cervical decompression surgery is associated with low mortality and morbidity, and results in clinical improvement in most dogs. The procedure seemingly does not result in syrinx collapse and resolution. Clinical improvement may not be sustained and some dogs can be expected to deteriorate. CLINICAL RELEVANCE: Cranial cervical decompression surgery may have a role in management of CM/SM. In dogs with severe pain, it can improve quality of life for several years; however, it does not appear to adequately address the primary cause of syringomyelia. Further prospective study is needed to better understand the pathogenesis and treatment of this disorder. Because this condition causes neuropathic pain but does not necessarily result in euthanasia more information is needed on appropriate pain management for these patients.

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.

Magnetic resonance imaging of articular process joint geometry and intervertebral disk degeneration in the caudal lumbar spine (L5-S1) of dogs with clinical signs of cauda equina compression.

The geometry of the lumbosacral region has been suspected to play a role in the development of degenerative lumbosacral stenosis in the dog. In this study, 50 dogs (21 German Shepherd dogs and 29 dogs of other breeds) with clinical signs of cauda equina compression were studied by magnetic resonance (MR) imaging. The orientation of the articular process joints in the L5-S1 region and the angle difference between two adjacent motion segments were calculated. Intervertebral disc degeneration of the same region was identified and classified in four stages. A positive association between MR-imaging stage and articular process joint angle difference in the transverse plane was found in the two groups of animals. German Shepherd dogs and dogs of other breeds had different geometry of the lumbosacral region with different articular process joint angles in the transverse plane and statistically different stages of disc degeneration.

[Cauda equina compression syndrome (CECS): retrospective study of surgical treatment with partial dorsal laminectomy in 86 dogs with lumbosacral stenosis]. / Beitrag zum Cauda equina Kompressionssyndrom (CEKS): retrospektive Studie über die chirurgische Therapie mit der partiellen dorsalen Laminektomie an 86 Hunden mit einer Lumbosakralstenose.

We report our results of partial lumbosacral laminectomy for treatment of canine Cauda equina Compression Syndrome due to a lumbosacral stenosis. Opposite to conventional techniques of dorsal laminectomy, only widening of the Spatium interarcuale is performed. This is achieved by exstirpation of the Lig. flavum and partial dorsal laminectomy of the first sacral segment. The Proc. spinosi and integrity of facet joints are fully maintained by this technique. In 96.5% of 86 dogs treated with this method relief of dorsal pressure and permanent rapid regression of clinical symptoms was achieved. In two cases recurrence of clinical symptoms was observed during follow up and one case showed no improvement at all. In conclusion partial dorsal laminectomy is a minimal invasive technique for treatment of Cauda equina compression syndrome expressed by pain reaction accompanied by minor neurological deficits caused by lumbosacral stenosis. Maintained spinal stability allows short reconvalescence and the unrestricted use of dogs immediately post operation.

Histopathologic changes in oculomotor nerve and ciliary ganglion in aneurysmatic compression injuries of oculomotor nerve.

BACKGROUND: Bilateral common carotid artery ligation (BCCAL) increases vertebrobasilar blood flow and leads to increased luminal pressure, luminal enlargement, wall thinning, convolutions and sometimes aneurysm formation in posterior circulation arteries, especially the posterior communicating arteries (PcomA). PcomA aneurysms compress the oculomotor nerves. The principal aim of this investigation is to examine the histopathologic results of the compressive effect of PcomA aneurysms on the oculomotor nerves (OMN) and on ciliary ganglions (CG). METHODS: When we observed the effects of BCCAL on the posterior circulation arteries of the brain in fifteen ligated rabbits after sacrifice, we noticed aneurysm formation on these arteries in three rabbits. These aneurysms developed on the PcomAs compressed the oculomotor nerves. These compressed nerves and normal oculomotor nerves together with their ciliary ganglions were examined histopathologically. RESULTS: A PComA aneurysm developed in three rabbits from 15 ligated animals and these aneurysms compressed the oculomotor nerves on the same side. Partial peripheral necrosis and axonal loss were seen on the compressed oculomotor nerves. Concomitantly, cellular loss and necrosis were also observed on their ganglions. CONCLUSION: Bilateral common carotid artery ligation may lead to PcomAs and these aneurysms could compress the oculomotor nerves. Compression injuries of oculomotor nerve may cause cellular injury and necrosis on both oculomotor nerves and ciliary ganglions.

Reversal of neurologic deficit in an adult gorilla with severe symptomatic lumbar stenosis.

STUDY DESIGN: A case report is presented. OBJECTIVE: To describe a case of severe symptomatic lumbar stenosis in an adult gorilla successfully treated with decompressive surgery. SUMMARY OF BACKGROUND DATA: Although spinal degenerative disease is thought to be less common in apes than in humans, gorillas and bonobos are known to have higher rates of disease than other African apes. METHODS: A 42-year-old female gorilla presented with a history of progressive lower extremity weakness. She was unable to ambulate normally or climb, pulling herself around with her arms. Her keeper did not believe she was incontinent. Physical examination revealed that ankle plantarflexion and dorsiflexion were absent on the right and weak on the left. Radiographs revealed disc space narrowing with osteophytes at the last mobile segment. Myelogram and computed tomography revealed severe spinal stenosis at the last two mobile segments. Under general anesthesia, a standard laminectomy and bilateral lateral recess decompression were performed. RESULTS: There were no anesthetic or wound complications. The gorilla was noted to have improved ankle strength bilaterally on postoperative day 1. On postoperative day 3, the animal began to walk and climb. At 20 months, the animal is back to her neurologic baseline. CONCLUSIONS: Symptomatic lumbar degenerative disease with neurologic compromise may be treated surgically, with excellent outcome, in the adult gorilla. Though this is an unusual situation, knowledge that this is a potentially reversible condition may benefit other gorillas in captivity.

The lumbosacral junction in working german shepherd dogs -- neurological and radiological evaluation.

The clinical and radiological incidence of lumbosacral (LS) disease was studied on 57 German Shepherd dogs (GSDs) used in active service. The study included a clinical history, a neurological examination, and plain radiographs of the caudal lumbar vertebrae. The neurological examinations revealed lower back pain and/or neural deficits in 21 dogs, of which 14 had a history of pain or pelvic gait abnormalities. Radiographic findings were spondylosis at L7-S1, degeneration of L7-S1 disc, LS malalignment, transitional LS vertebrae and/or primary spinal canal stenosis in 15 dogs with neurological abnormalities and/or back pain and in 18 dogs with no clinical signs. No correlation between the neurological and the radiographic findings were found. This study demonstrates that even prominent radiographic LS abnormalities are of minimal value in the evaluation of LS disease in the GSD.

Association of cauda equina compression on magnetic resonance images and clinical signs in dogs with degenerative lumbosacral stenosis.

Magnetic resonance imaging (MRI) was used to examine the lumbosacral spine of 27 dogs with degenerative lumbosacral stenosis. Four normal dogs were also similarly imaged. Compression of the soft-tissue structures within the vertebral canal at the lumbosacral space was assessed in two ways: by measuring dorsoventral diameter on T1-weighted sagittal images and cross-sectional area on transverse images. The severity of the clinical signs was compared to the severity of cauda equina compression. No significant correlation was found. It is concluded that degree of compression as determined by MRI at time of presentation is independent of disease severity.

Fracture of L7 vertebral articular facets and pedicles following dorsal laminectomy in a dog.

A 6.5-year-old German Shepherd Dog underwent decompressive surgery for cauda equina syndrome. On the basis of intraoperative findings, the dorsal laminectomy was extended from L6 to S2. Partial dorsal annulectomies were also performed on the L6-7 and L7-S1 intervertebral disks. Two weeks following discharge, the dog had an acute onset of signs of pain and worsening of the neurologic status. Radiography and surgical exploration revealed bilateral fractures of the vertebral pedicles and caudal articular facets of L7. Vertebral stabilization was achieved with intramedullary pins and methylmethacrylate. The dog fully recovered. Although the destabilizing effect of various procedures on the vertebral column has been documented in vitro, vertebral fractures associated with instability have not been reported. Our description of a vertebral fracture following a cauda equina decompressive procedure in a dog emphasizes the need for caution when performing multi-level dorsal laminectomy and diskectomy.

Lumbosacral osteochondrosis: radiological features and surgical management in 34 dogs.

Lumbosacral osteochondrosis has been diagnosed with increasing frequency over the past few years. Nevertheless, poor recognition of the condition continues to lead to frequent misdiagnosis. A study was therefore undertaken over a 12-year period (1986 to 1998) to describe the use of a variety of radiological studies to define the syndrome and the use of different surgical techniques for optimal treatment of the condition. Dogs with clinical signs of cauda equina neuropathy and radiological signs of lumbosacral osteochondrosis were older than 14 months (mean age 6.3 years). German shepherd dogs, boxers and rottweilers were heavily represented. Of the 34 dogs with osteochondrosis in this study, the lesion appeared to be related to the sacrum in 31 dogs (91 per cent) and the seventh lumbar vertebra in the remaining three dogs (9 per cent). Twenty-seven male and seven female dogs were affected (4:1). Out of the 34 dogs, six (18 per cent) were treated conservatively and the remaining 28 (82 per cent) were treated surgically. The outcome of surgical treatment was considered to be satisfactory in 24 (86 per cent) of these latter dogs.

Transitional lumbosacral vertebral anomaly in the dog: a radiographic study.

Transitional lumbosacral vertebral anomalies have for some time been suggested as a possible cause of cauda equina syndrome (especially in the German shepherd dog [GSD]), a condition recently thought to be inherited. The frequency of this condition within a large clinical population and the radiographic features used in its detection are reported. In a group of 143 patients, the sexes were similarly represented and the GSD was greatly overrepresented. The anomaly is characterised by separation of the first sacral segment that was identified on the lateral view by the presence of a radiolucent disc space between what are normally the first and second sacral segments. On the ventrodorsal view, the anomaly was characterised by separation of the spinous processes between what are normally the first and second sacral segments. In the presence of the transitional segment, the nature of the sacroiliac joint at the level of the anomalous segment varies from a strong ilial attachment, with the presence of a wing-like lateral process, to a weakened ilial attachment because of the presence of a lateral process, shaped as that seen on a lumbar segment. These patterns were present unilaterally or bilaterally and result in symmetrical or asymmetrical patterns. The effect of the weakening of the sacroiliac attachment was thought to result in premature disc degeneration, which, together with spinal canal stenosis, resulted in potential compression of the overlying spinal nerves and creation of a cauda equina syndrome. The condition is thought to have clinical significance and should be selected against in breeding, especially in the GSD.

A review of imaging techniques for canine cauda equina syndrome.

There are many imaging modalities available for evaluating the canine lumbosacral region. These include conventional radiography, stress radiography, myelography, epidurography, transosseous and intravenous venography, discography, linear tomography, computed tomography, and magnetic resonance imaging. Myelography, epidurography and discography are commonly used, but often lack sensitivity. Myelography is of little value when evaluating the cauda equina because the dural sac is elevated from the vertebral canal floor and frequently ends before the lumbosacral junction. Epidurography will identify a ventrally located compressive lesion and discography can delineate the dorsal extent of the diseased disc; however, both are sometimes difficult to interpret. Therefore, more than one of these imaging techniques must be used in order to make a diagnosis. Computed tomography and magnetic resonance imaging have become valuable in evaluating the lumbosacral region in dogs. These modalities have proven to be both sensitive and specific for determining cauda equina compression in both humans and in dogs.