Current Strategies for Management of Intervertebral Disc Disease

Home , Intervertebral disc, Paresthesia, Veterinary surgery

Current Strategies for Management of Intervertebral Disc Disease.

Ashley Bensfield, DVM, DACVIM (Neurology) Objectives

• Pathophysiology/terminology • Where the confusion about IVDD comes from • Diagnostics • Treatment options • Prognosis Pathophysiology/Terminology

• Type of Intervertebral Disc Disease . Hansen Type I . Hansen Type II . Hansen Type III • Myelopathy –spinal cord dysfunction • Spinal Hyperesthesia – misused, but accepted . abnormal pain on spinal palpation. . Synonym - hyperpathia IVDD

Hoerlein 447 Pathophysiology/Terminology

• Upper motor neuron deficits – spastic, normo- to hyperreflexive • Lower motor neuron deficits – Decreased tone, normo- to hyporeflexive. • Nociception – conscious perception of painful stimulus • Withdrawal Reflex– Reflexive flexion of limb with noxious stimulus to toe Spinal Reflex Arc

Platt 21 Pathophysiology/Terminology

• Superficial pain perception . Conscious response to mildly noxious stimulus • Light pinch, needle prick • Deep pain perception . Conscious response to bone crushing pain. • Paresis – inability to move body part with appropriate strength Pathophysiology/Terminology

• Plegia – paralysis – inability to move body part • Ataxia – impaired coordination of movement . Proprioceptive . Vestibular . Cerebellar • Proprioception – knowledge of where body parts are in space w/o having to look at them. Why is IVDD so confusing?

• Impossible to find all the information in one place • Numerous persistent incorrect anecdotal practices - e.g.: . Surgery not needed unless paralyzed . Medical management should be tried/failed before surgery considered . IVDD is not a systemic disease . Length of medical management time is arbitrary References – This is a partial list!

• Brisson, B et al. “Comparison of the effect of single-site and multiple-site disk fenestration on the rate of recurrence of the thoracolumbar intervertebral disk herniation in dogs.” J Am Vet Med Assoc 2001; 238: 1583-1600. • Brisson, B et al. “Recurrence of thoracolumbar intervertebral disk extrusion in chondrodystrophic dogs after surgical decompression with or without prophylactic fenestration: 265 cases (1995-1999).” J Am Vet Med Assoc 2004; 224: 1808-1814. • De Risio, L et al. “Association of clinical and magnetic resonance imaging findings with outcome in dogs with presumptive acute noncompressive nucleus pulposus extrusion: 42 cases (2000-2007).” J am Vet Med Assoc 2009:234:495-504. • Flegel, T et al. “Partial Lateral Corpectomy of the Thoracolumbar Spine in 51 Dogs: Assessment of Slot Morphometery and Spinal Cord Decompression.” Veterinary Surgery, 40 (2011) 14-21. • Forterre, F et al. “Microfenestration Using the CUSA Excel Ultrasonic Aspiration System in Chondrodystrophic Dogs with Thoracolumbar Disk Extrusion: A Descriptive Cadaveric and Clinical Study.” Veterinary Surgery, 40 (2011) 34-39. • Gomes, SA, et al. “Clinical and magnetic resonance imaging characteristics of thracolumbar intervertebral disk extrusions and protrusions in large breed dogs.” Vet Radiol Ultrasound, Vol. 00, No. 0, 2016, pp 1-10. • Hecht, S. et al. “Myelography vs. computed tomography in the evaluation of acute thoracolumbar intervertebral disk extrusion in chondrodystrophic dogs.” Veterinary Radiology & Ultrasound, Vol. 50, No. 4, 2009, pp 353-359. • Hoerlein, BF. Canine Neurology: Diagnosis and Treatment, 3rd Ed. W. B. Saunders Company. Philadelphia. 1978 • Israel, SK et al. “Relative sensitivity of computed tomograpny and myelography for identification of thoracolumbar intervertebral disk herniations in dogs.” Veterinary Radiology & Ultrasound, Vol. 50, No. 3, 2009, pp 247-252. • Jeffrey, N et al. “Factors associated with recovery from paraplegia in dogs with loss of pain perception in the pelvic limbs following intervertebral disk herniation.” J Am Vet Med Assoc 2016;248:386-394. • Jensen, VF, et al. “Quantification of the association between intervertebral disk calcification and disk herniation in Dachshunds.” J Am Vet Med Assoc 2008; 233:1090-1095. • Levine, JM, et al. “Magnetic Resonance Imaging in Dogs with Neurological Impairment Due to acute Thoracic and Lumbar Intervertebral Disk Herniation.” J Vet Intern Med. 2009; 23: 1220-1226. • McKee, WM, et al. “Presumptive exercise-associated peracute thoracolumbar disc extrusion in 48 dogs.” Veterinary Record (2010)166, 523-528. • Olby, NJ, et al. “Prevalence of Urinary Tract Infection in Dogs after Surgery for Thoracolumbar Intervertebral Disc Extrusion.” J Vet Intern Med 2010;24: 1106-1111. • Platt, S and N Olby. BSAVA Manual of Canine and Feline Neurology, 4th Ed. BSAVA. Glouchester. 2013 • Sharp, NJH and Simon Wheeler. Small Animal Spinal Disorders: Diagnosis and Surgery, 2nd Ed. Elsevier Mosby. Philadelphia. 2005 • Taylor-Brown, FE, and Steven De Decker. “Presumptive acute non-compressive nucleus pulposus extrusion in 11 cats: clinical features, diagnostic imaging findings, treatment and outcome.” Journal of Feline Medicine and Surgery. 2017, Vol 19 (1) 21-26. Hansen Type I IVDD

• Herniation, rupture, extrusion of nucleus pulposus through a tear in the annulus pulposus . Abnormal/unhealthy nucleus pulposus material, unable to withstand normal forces . Mineralized nucleus pulposus • chondroid degeneration Hansen Type I IVDD

• Pain and paresis/plegia caused by: . compression of spinal cord and nerve roots . Bruising type injury to spinal cord . Pain from stretching/tearing of disc annulus and dorsal longitudinal ligament Hansen Type III IVDD

• Catch all phrase • Rupture of IVDD capsule under pressure (traumatic) with explosive extrusion of nucleus pulposus. • Synonyms: . High Velocity Low Volume Extrusion, Missile Disc, Acute Non-compressive Nucleus Pulposus Extrusion (ANNPE), . Splatter disc (overlaps with Type I), Liquid Disc Type I and III IVDD Signalment

• Peracute to gradual (days) onset • Spinal hyperesthesia • Abnormal posturing • Muscle spasms • Paresis/paralysis • +/- abnormal reflexes • +/- decreased or absent nociception Type I and III IVDD Signalment

• Young (4-6y) chondrodystrophic dog breeds, and middle aged (6-8) non-chondrodystrophic. . In young dachshunds – association btwn number of mineralized discs on radiographs and risk for future Type I IVDD • Young to middle aged cats • Type III associated with exercise/activity . Similar presentation to FCE and/or spinal trauma Neurolocalization

• UMN signs generally carry a better prognosis than LMN signs. . LMN signs - dysfunction of spinal cord intumescence (neuron cell bodies for the LMNs reside). • Damage to cell body results in permanent loss of that neuron. . UMN signs – axon damage/dysfunction. • Spinal cord/nerve axons have much greater ability to regenerate/resist injury. • Hyperesthesia – if present, site of pain usually indicates location of IVDD. • Cutaneous Trunci reflex – 1-2 segments caudal to site of injury Schiff-Sherrington Posture

• Acute thoracolumbar junction spinal cord injury . Loss of upper motor neuron inhibition to forelimbs  Increased extensor tone in forelimbs • Forelimb proprioception, voluntary motor and reflexes normal to increased . Mistaken for Opisthotonos • SSP – no central vestibular or RAAS signs. . Does not give information about prognosis. Platt 6 Nerve Root Signature

Sharp 93 Myelomalacia

• “Spinal cord” – “Softening” . Ischemic death of the spinal cord . Can be focal, but often progresses to the “ascending- descending” form. . Fatal due to progression cranially to the areas of the spinal cord controlling respiratory muscles • Occurs in 10% of patients with acute paraplegia and loss of nociception . May not manifest for up to 7-10 days (usually under 5) . No treatment, including surgery, shown to prevent. Myelomalacia

• Clinical signs . Ascending cutaneous trunci reflex cutoff • This reflex should not decrease further after 24hrs post- op or post-disc extrusion. • Track daily by marking patient’s back with permanent marker . Flaccid abdomen and pelvic limbs . Patient appears restless/uncomfortable . May be hyper- or hypothermic . Progressive respiratory paralysis Sharp 128 Hansen Type II IVDD

• Thickening and protrusion of annulus fibrosus • Fibrous metaplasia of nucleus pulposus • May be associated with spondylosis deformans (ankylosing). • Paresis caused by compression of spinal cord and/or nerve roots. . May result in spinal cord gliosis and nerve atrophy • Pain caused by nerve root compression Type II IVDD Signalment

• Older, generally large breed dogs or older cats • Chronic slowly progressive paresis +/- spinal pain . Often reluctant to jump or use stairs . “getting old,” “slowing down.” • Can acutely worsen • +/- nerve root signature or paresthesia Differential Diagnoses

• Other causes of pain and/or myelopathy . FCE, spinal fracture, discospondylitis, neoplasia, myelitis (infectious/auto-immune), Deg. Myel., COMS. • Other causes of LMN weakness . Neuropathy, myopathy, junctionopathy (MG), electrolyte disturbances, diabetes mellitus, plexus avulsion. • General causes of weakness . Hypotension, hypoglycemia, hemoabdomen, etc. • Orthopedic disease/joint pain . Bilateral CCL disease, hip dysplasia, polyarthropathy Diagnostics – Physical Exam

• General PE . Back pain and abdominal pain can be hard to differentiate . Particular attention to causes of weakness • Thorough auscultation, palpate pulses, ballotte abdomen, check MM color. . Thorough orthopedic exam Diagnostics-Neurological Examination

• Importance of performing neuro exam on normal patients. . Make sure patient adequately supported to differentiate weakness from CP deficit. • Should be mentally appropriate • Cranial nerves – Possible Horner’s Syndrome if cervical/high thoracic. Otherwise normal. • Nociception-if limbs move voluntarily, pain sensation should be present – no need to aggressively test. . Reflex does not equal nociception! • Remember tail/perineum! Diagnostics- Neurological Examination

• Spinal palpation, neck range of motion . If suspect animal is painful, do this step last! . Neck pain and partial seizures can look similar . Neck pain dogs will hunch their T/L spine too. • Voluntary Motor assessment • Assess patients in quiet room . On the floor . Good footing

Olby Fig.7-2, 3rd Ed Diagnostics – Minimum Database

• Complete blood count (with manual diff) • Chemistry profile (with CPK) • Urinalysis (with sediment) • +/- Tick testing • Aspergillus antigen German Shepherds • DM genetic test – Boxers, GSD, Corgi • +/- Neoplasia screening if over 8yrs (3-view CXR/AUS) • Viral testing for cats. • ECG/BP if renal dz, arrhythmia, poor pulses, etc. Diagnostics - Imaging

• Radiographs . Low yield for IVDD . Provides information about • Congenital malformations • Spinal fracture • Osteolytic disease – cancer, osteomyelitis, discospondylitis, etc. . V/D views less helpful, especially if not sedated . COLLIMATE – not a time for cat/dog-o-gram Diagnostics - Myelography

• Technically challenging but inexpensive. • General anesthesia, iodinated compound injected into epidural space. . Causes reactive meningitis x 2 weeks and small area of permanent focal damage to lumbar spinal cord where needle penetrates. . May cause seizures • Highlights extradural compression . Does not always provide accurate side/site . Does not give information about health of spinal cord. . Helpful in evaluating Type II IVDD for dynamic compression . Does not differentiate neoplasia, etc. from IVDD. Diagnostics – CT +/- myelography

• Rapidly identify acute, compressive, Type I, thoracolumbar IVDD in young dogs. . Site, side, extent • Not as helpful for differentiating acute/chronic sites. • Does not provide information about health of spinal cord. • More expensive than myelography, less expensive than MRI • Helpful in evaluating Type II lesions for dynamic compression with myelography. • Does not always differentiate IVDD from neoplasia, etc. . IV contrast administration can help. Hansen Type I IVDD Hansen Type I IVDD Diagnostics - MRI

• Best modality for evaluating IVD, spinal cord, and nerve roots . Not as good bone detail as CT. . Evaluates spinal cord for edema/gliosis. • More prognostic information than CT or myelography . More readily differentiates acute vs. chronic sites. . Can evaluate dynamic compression • More time consuming and expensive than myelography or CT. Hansen Type I IVDD Hansen Type II IVDD Treatment options – Medical

• Type I . Rest, anti-inflammatory medication, pain management, bladder management • 6 weeks cage rest, no jumping/stairs for life • NSAID OR anti-inflammatory dose of steroids – 10-14 days only. • Manage secondary damage – hydration, free radicals, etc. • +/- muscle relaxer, opioid, and/or gabapentin • +/- bladder management – U-cath, intermittent catheterization, manual expression. – Prazosin (1mg/15kg TID) +/- diazepam, +/- bethanechol Treatment Options - Medical

• Type II . Physical therapy and/or intermittent cage rest. . Long term vs. pulse anti-inflammatory medications . Long term gabapentin and/or tramadol. . No jumping or stairs . +/- bladder management Treatment Options - Surgical

• Hemilaminectomy • Dorsal Laminectomy • Lateral Corpectomy • Ventral Slot • Distraction/fusion • Fenestration – Reduces risk of future Type I Treatment – Post-OP

• 2-4 weeks strict rest, no jumping/stairs for life • Gradual return to walking, then running, and playing. • Anti-inflammatory therapy x 10-14 days • Tramadol, gabapentin as needed • Muscle relaxer – diazepam, methocarbamol, 5-7 days Treatment Options - Complementary

• Acupuncture • Laser Therapy – for muscle soreness. • Physical therapy – when? How much? • Massage • Ice/Hot packing Prognosis Type I or III, acute

Neuro- Pain + Medical Pain + Sx Pain - Medical Pain - Sx localization C1-C5 50 %, 30-50% 90-95% N/A N/A Relapse C6-T2 50%, 30-50% 70-95% N/A N/A Relapse T3-L3 70%, 30% 90-95% 10% 50-55%, Relapse Timing??? L4-S1 50-70%, ~50% 70-90% Less than 10% 10-30%, relapse Timing???

**with pain +, no change in prognosis for surgical success ~8wks from time of injury. However, if become pain -, prognosis decreases as above.** Prognosis Type I, chronic, pain +

• Because of additional scar tissue, prognosis with surgery decreased by about 20-25% if surgery performed >8wks after herniation Prognosis Type II

• Degree of spinal cord atrophy difficult to quantify. . No improvement in neurological grade with surgery if due to atrophy . Decreased functional reserve • More likely to be worse following surgery – Minor trauma during surgery = “last straw effect” • Surgical vs. conservative management have similar outcomes . Indications to try surgery • Chronic pain • Paralysis • Improved neurological grade with anti-inflammatories. • Owner goals – try to prevent further worsening knowing risk References

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