January, 2000

Background   Physical Examination   Neurology Examination Results   Tests Performed   Summary    Appendix

Background

This dog was seen at the Veterinary Medical Teaching Hospital, University of California Davis. We are grateful for the skillful participation of the Radiology Service, Clinical Laboratories and Electrodiagnostic Laboratory of the Neurology/Neurosurgery Service in the diagnostic investigation of this dog.

Signalment

Labrador X, castrated male, 12 years old.

History

Left pelvic limb lameness for 18 months, after being stepped on by a horse. Immediately after the injury, he dragged the toes of the left pelvic limb when walking. Medical management at the time consisted of strict rest, non-steroidal anti-inflammatory drugs, and acupuncture. Although the lameness never resolved completely, it appeared static. The owner reports that during the last thirty days there has been an increase in the lameness and muscle atrophy in the left pelvic limb.

Medication

The dog is not presently receiving medication.

Past Medical History

At one year of age the dog was diagnosed as having coccidioidomycosis by means of a bone biopsy of the right hock and was treated with Ketoconazole for two years.

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Physical Examination (only abnormal findings are noted)

 General: Alert and responsive; Body condition score=6. (System range=1-9)

 Rectal temperature: 38.0 (100.4F)

 Heart Rate: 87/m, normal rhythm, femoral artery pulses equal and synchronous.

 Respiratory Rate: 22/m

 Mucosae: pink, capillary refill time: < 2 sec.

 Integument:

 EENT: corneal dystrophy, OU

 Cardiopulmonary: Grade II/VI holosystolic murmur, Point of maximal intensity: mitral valve.

 Abdominal cavity:

 Musculoskeletal: Muscle atrophy of entire left pelvic limb.

 Lymph nodes:

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Neurological Examination Results

 Consciousness: Alert, responsive.

 Posture: Normal

 Falling: Absent

 Righting reactions: Normal

 Head Tilt: None

 Tremor: None

 Gait: See video   

 Circling: None observed

 Paresis: Not apparent.

 Postural and Placing Reactions: Normal

 Spinal (segmental) reflexes: (N=normal; D= depressed; A= Absent; I= increased;)

 Tendon Reflexes
Forelimb: N: Extensor Carpi: N: Biceps brachii: N; Triceps brachii: N
Pelvic limbs: Quadriceps: N; Gastroc/Dig. flexors: N.

 Flexion Reflexes: Forelimbs: N; Pelvic limbs: N.

 Crossed Extensor Reflexes: Forelimbs: Not present clinically; Pelvic limbs: Not present clinically.

 Perineal Reflexes: N

 Cutaneous Trunci Reflexes: Present in all normal segmental levels.

Cranial Nerves

 I: Not tested

 II: Vision apparently normal

 III, IV, VI: Pupils equal, normal direct and indirect pupillary light reflexes. Normal ocular positions and physiological nystagmus

 V: Sensory: N Motor: N

 VII: Sensory: N; Muscles of facial expression N

 VIII: Righting reactions: N; Spontaneous nystagmus: absent; Positional nystagmus: absent.

 VII: Vision menace - Nystagmus, resting VIII - Nystagmus

 IX, X: Gag reflex normal and symmetrical

 XII: Tongue: position, symmetry, normal movements

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Tests Performed

Hematology, Chemistry and Urinalysis

General Clinical Chemistry Panel Results

Hemogram Results

Immunology, Serology and Microbiology Tests

Fungal Serology Report: Coccidioides immitis

Cerebrospinal Fluid Studies

Cerebrospinal Fluid: Total and Differential Cell Counts; Total Protein

 Fluid from: Lumbar region

 Gross appearance: Hazy, colorless

 Refractive index: 1.3350

 Total erythrocytes: 1400/uL

 Total nucleated cells: < 1/uL

Differential Nucleated Cell Counts:

 Neutrophils: 88%

 Small mononuclear cells: 0%

 Large mononuclear cells: 6%

 Eosinophils: 6%

Clinical Neurophysiological Examinations

Motor Conduction Velocity

Click on the image to see a larger view

The left superficial peroneal nerve and its proximal extensions were stimulated at the sites shown. Stimulation at the hip was repeated, yielding a second trace for convenience in measuring latency from the hip to the hock. (L1, L2: points where latency was measured.) Conduction velocities (meters/sec): hock to muscle: 17.5 stifle to hock: 36.2 hip to stifle: 41.6 hip to hock: 39.0 See "Recording and Stimulation Methods" below

Sensory Conduction Velocity and Cord Dorsum Potential (CDP) Recordings

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The left dorsal metatarsal nerve 3/4 was stimulated while recordings were made simultaneously at the hock, stifle, hip and interarcuate space of the L3/L4 vertebrae. 1000 responses were averaged. The low amplitude of the potential at the hip is an artifact caused by technical problems. The other potentials are of normal amplitude. The two major peaks of the CDP are unusual. Conduction velocities in meters/second were: Stimulus site to hock: 47.5 Hock to stifle: 51.4 Stifle to hip: 69.4 Hock to hip: 59.8 See "Recording and Stimulation Methods" below

Electromyography Report

Bipolar, coaxial needle electrodes were used to record the EMG of the head, limbs and paraspinal muscles (see List of muscles tested below). No abnormalities were detected.

Muscles Examined and Findings

Please note: only abnormal findings are included.

Imaging tests - Radiographs

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Survey Radiographs of entire spine

Myelograms of entire spine

Lumbosacral Study

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Other Radiographs

Ventrodorsal radiograph of thorax of VNN Case of the Month, January 2000. No additional radiographs are available in the category "other radiographs".

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Summary

Click on the image to see a larger view    

The clinical signs, clinical neurophysiology and imaging in this case are consistent with a diagnosis of radiculopathy associated with degenerative lumbosacral stenosis. The discogram (see at right ) demonstrates that the contrast material is contained within the anulus and the anulus is bulging dorsally.

The lesions seen in the lumbosacral region, and the clinical signs they cause, often differ from those seen at other locations of the spine because of the unique structure of the region. The neurological signs and apparent pain result from nerve root compression and meningeal irritation; however some evidence supports a role for discogenic pain also. Lumbosacral stenosis is most commonly associated with Hansen's type II disc degeneration and protrusion.

Male, middle aged, large breed dogs are most often affected; however degenerative lumbosacral stenosis can occur in small breed dogs and in cats also. The clinical signs may be acute or chronic, continuous or intermittent and may vary greatly. They include but are not limited to reluctance to jump or climb stairs, altered tail carriage, pelvic limb lameness, and hyperesthesia on palpation of the lumbosacral area. More severe neurological deficits may include pelvic limb proprioceptive deficits, decreased withdrawal and perineal reflexes, and urinary and fecal incontinence.

Diagnostic techniques used include imaging and electrodiagnostic testing. Plain radiographs, contrast studies (myelography, epidurography and discography), stressed flexion and extension techniques are employed routinely as well as advanced imaging, computerized tomography and magnetic resonance imaging. Electromyography and spinal cord-evoked potentials provide important information and have been reported to increase diagnostic accuracy in cases involving cauda equina compression.

Several treatment options with varying degrees of success have been reported for degenerative lumbosacral stenosis. These range from rest and medication to surgical procedures that may include one or a combination of the following: dorsal laminectomy, foraminotomy, facetectomy, disc fenestration, and stabilization techniques. For additional information on degenerative lumbosacral stenosis, its diagnosis, and its treatment, please see the references.

References

1.  Adams, W. H., Daniel, G.B., Pardo, A.D., Selcer, R.R.. Magnetic Resonance Imaging of the Caudal Lumbar and Lumbosacral Spine in 13 Dogs (1990-1993). Veterinary Radiology & Ultrasound, 1995,36 (1), 1-13.

2.  Danielsson, F., Sjo..sto..m, L. Surgical Treatment of Degenerative Lumbosacral Stenosis in Dogs. Veterinary Surgery, 1999, 28, 91-98.

3.  Morgan, J.P., Bailey, C. S., Cauda Equine Syndrome in the Dog: Radiographic Evaluation. Journal of Small Animal Practice, 1990, 31, 69-77.

4.  Ramirez, O., Thrall, D.E., A Review of Imaging Techniques for Canine Cauda Equina Syndrome. Veterinary Radiology & Ultrasound, 1998, 39 (4), 283-296.

5.  Sisson, A.F., LeCouteur, R.A., Ingram, J.T., Park, R.D., Child G. Diagnosis of Cauda Equina Abnormalities By Using Electromyography, Discography, and Epidurography in Dogs. Journal of Veterinary Internal Medicine, 1992, 6, 253-263.

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Appendix

RECORDING AND STIMULATION METHODS

I. Electromyography is performed using bipolar coaxial needle electrodes connected to either a Nihon-Kohden Neuropack 4 recording system or a Nicolet Viking 3 system.

II Motor and Sensory Nerve Conduction Velocities

A. Tibial nerve motor nerve conduction velocity. A needle exploring electrode is placed in the interosseus muscles and a reference electrode in the distal metatarsal region; stimuli are applied to the nerve at the hock, stifle and hip.

B. Peroneal motor and sensory nerve conduction velocities in the rear legs are routinely measure using the method of Niederhauser (Niederhauser and Holliday, 19 ; Niederhauser et al., 19 ). In this method, motor conduction velocity (MCV) is determined first as follows: needle electrodes are used to stimulate the superficial peroneal nerve near the hock and also near its origins in the peroneal nerve, at the stifle and hip. For recording, the exploring electrode (needle) is located in the extensor digitorum brevis muscle on the dorsolateral aspect of the metatarsus and the reference electrode is located subcutaneously, near the tendon of insertion of this muscle, just proximal to the metatarso-phalangeal joint.

The minimal stimulus intensity sufficient to elicit a maximal action potential is then found for each stimulus site; this is usually less than 5 mA. The cathodal electrodes are then left in place and used as exploring electrodes for recording the sensory nerve action potentials.

Sensory nerve action potentials at the three sites and cord dorsum potentials at a fourth site are recorded simultaneously. The dorsal metatarsal nerves are stimulated with subcutaneous needle electrodes placed at the level of the fourth metatarsal bone, about 1cm proximal to the metatarsophalangeal joint . The cathode and the anode are placed 5-7 mm apart on opposite sides of the nerve. By taking care to assure proximity of the electrodes to the nerve when recording MCV (described above), robust sensory nerve action potentials can be recorded readily. Exceptions occur in large dogs, where optimal recordings at the hip or stifle are sometimes difficult or impossible to achieve, and in some dogs with severe neuropathies where the disease has caused low amplitude by deleting axons and/or causing severe dispersion of the action potentials.

For recording cord dorsum potentials (CDP), exploring electrodes are placed percutaneously in the dorsal midline with the needle tip in proximity to the interarcuate ligament of fourth and fifth lumbar vertebrae. Reference electrodes are placed subcutaneously, 3-cm lateral to active electrodes.

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