What Is Your Neurologic Diagnosis? - AVMA Journals

What Is Your Neurologic Diagnosis? Signalment: 10-year-old male neutered West Highland White Terrier. History: The dog had a 3-week history of severe tetraparesis. Annual vaccinations were current. Approximately 12 months previously, the dog developed lameness of the left forelimb, with no abnormalities detected radiographically in the limb or vertebral column. Carprofen (unknown dose and frequency) and other nonsteroidal anti-inflammatory drugs were administered and yielded limited improvement. Treatment with prednisone (1.0 mg/kg [0.45 mg/lb], PO, q 12 h) was initiated, and the dosage was tapered gradually to 0.84 mg/kg (0.38 mg/lb), PO, every 12 hours during the following 3 months. After initial improvement in lameness, the beneficial effects of prednisone diminished, and within 6 months the left forelimb lameness had progressed to left-sided hemiparesis. After 6 weeks, mild tetraparesis was observed, which progressed to nonambulatory tetraparesis 3 weeks later. Physical Examination: The dog was obese and tachypneic (120 breaths/min) and had nonambulatory tetraparesis (left side worse than right side). There were signs of lack of sensation in the left forelimb and signs of diminished sensation in the right forelimb. Organomegaly was evident on palpation of the cranial portion of the abdomen and an approximately 6- to 8-cm firm mass was detected in the left axillary region. Neurologic examination: Observation: Mental Posture Gait Paresis Other

Alert X Depressed Normal Head tilt Normal Ataxia Pelvic limbs Tetra X Nonambulatory; sternal recumbancy.

Disoriented Tremor Pelvic limbs Hemi

Stupor Falling All 4 X Mono

Coma Circling

Key: 4=exaggerated, clonus; 3=exaggerated; 2=normal; 1=diminished; 0=none; NE=not evaluated

Postural reactions Wheelbarrow Hopping Ext postural thrust Proprioceptive pos Hemistand/walk Placing–tactile Placing–visual

Spinal reflexes Quadriceps Extensor carpi Flexion Crossed extensor Perineal

LF 0 0

RF 0 1

0 0 1-2 1-2

0 0 2 2

LF

RF

1 1 0

0-1 0-2 0

Cranial nerves II, VII–Vision menace II, III–Pupils resting Stim L Stim R II–Fundus III, IV, VI–Strabismus, resting III, IV, VI, VIII–Strabismus, position

L 2 2 2 2 2 0 0

R 2 2 2 2 2 0 0

LR

RR

1 NE 0 0

1 NE 0 0

LR 3

RR 3

3 0 2

3 0 2

VIII–Nystagmus, resting VIII–Nystagmus, change V–Sensation VII–Facial mm V, VII–Palpebral flex IX, X–Gag XII–Tongue

L 0 2 2 2 2 2 2

R 0 2 2 2 2 2 2

Comments CN No abnormalities observed; 0 = absent (normal finding)

Sensation (Locate and describe abnormal) Hyperesthesia Superficial pain Cutaneous reflex Deep pain

Signs of discomfort when head was moved toward left. 2 0 No cutaneous trunci reflex evident. 2

What is the problem? Where is the lesion? What are the most probable causes of this problem? What is your plan to establish a diagnosis? Please turn the page. JAVMA, Vol 221, No. 10, November 15, 2002

Vet Med Today: What Is Your Neurologic Diagnosis?

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Assessment Anatomic diagnosis Problem

Rule out location

Nonambulatory tetraparesis

Cervicothoracic intumescence (C6 to T2 spinal cord segment).

Absence of cutaneous trunci reflex (bilateral)

Lateral thoracic nerve (C8 to T1 spinal cord segment).

Left forelimb sensation absent, right forelimb sensation diminished

Cervicothoracic intumescence (C6 to T2 spinal cord segment).

Likely location of one lesion -

C6 to T2 spinal cord segment.

Etiologic diagnosis Rule out disease process Neoplasia (especially nerve sheath tumor; primary or metastatic neoplasia) Degenerative lesion (especially intervertebral disk prolapse, denervation) Trauma Inflammatory-infectious (intervertebral disk space, vertebrae)

Diagnostic plan (in order of priority) CBC, platelet count, serum biochemical analyses, urinalysis, urine bacteriologic culture and susceptibility testing. Spinal, left forelimb, and thoracic radiography. Cytologic and histologic examination of axillary mass. Magnetic resonance imaging, electromyography, and myelography .

Comments: Because the dog had upper motor neuron signs to the hind limbs, lower motor neuron signs to the forelimbs, and had worse signs on the left side than on the right side, the lesion was localized to the C6 to T2 spinal cord segment (the cervicothoracic intumescence). A lesion cranial to the cervicothoracic intumescence would cause upper motor neuron signs to the fore- and hind limbs. A lesion caudal to T2 is also caudal to the cervicothoracic intumescence and would not affect the forelimbs. Between C8 and T1, lateral thoracic nerve roots exit the spinal cord and supply motor function to the cutaneous trunci muscle, the effector component of the cutaneous trunci reflex. In this dog, a lesion in the region of C8 to T1 was responsible for the absence bilaterally of the cutaneous trunci reflex. Horner’s syndrome (miosis, ptosis, enophthalmos, and protrusion of the third eyelid) was not observed, but may result from disruption of the preganglionic sympathetic innervation that originates from T1 to T3 spinal cord segments by lesions involving the more caudal portion of the cervicothoracic intumescence or the adjacent brachial plexus (a nerve plexus in the axillary region formed by the ventral branches of the C6 through C8 spinal nerves and the T1 and T2 spinal nerves). Test results: Abnormal laboratory data: Serum biochemical abnormalities included high alkaline phosphatase activity (660 U/L; reference range, 11 to 140 U/L) and high alanine aminotransferase activity (115 U/L; reference range, 10 to 90 U/L). These high enzyme activities could have been caused by treatment with prednisone. Imaging procedures: Radiographs of the thorax, vertebral column, and left forelimb revealed a soft tissue density in the left axillary region with no apparent bone involvement. Histopathologic findings: A 16-gauge core needle biopsya specimen was taken from the axillary mass; histologic examination revealed a poorly differentiated sarcoma. Presumptive diagnosis: Nerve sheath tumor involving the brachial plexus with involvement of the spinal cord at the level of C6 toT2. Prognosis with or without treatment: Poor. Therapeutic plan: None. Surgical intervention and radiotherapy were discussed with the owners, and further diagnostic and treatment procedures were declined. Outcome: The dog was euthanatized. At necropsy, a 5 X 5 X 7-cm round, firm, pale, lobulated, expansive, invasive mass was found in the left axillary region (Fig 1). The mass extended into the cervical spinal nerve roots of C6 and C7, with invasion of the spinal cord at these segments (Fig 2). Invasion and compression of the caudal portion of the cervical spinal cord by a 5 X 10-mm pale, firm, lobulated mass was observed. Histologically, the mass was a poorly differentiated (anaplastic) spindle-cell sarcoma; it lacked the consistent patterns and differentiation required to define the histogenesis of the tumor. Discussion: This dog’s history of forelimb lameness that, during 12 months, progressed to signs consistent with spinal cord compression is typical of that of peripheral nerve sheath tumors.1-3 In animals, tumors arising from the nerve sheath may be classified as either peripheral nerve sheath tumors or malignant peripheral nerve sheath tumors; descriptive terms such as schwannoma, neurofibroma, neurinoma, neurilemmoma, and their malignant counterparts have more application in human medicine.4,5 Malignant peripheral nerve sheath tumors may be 1398


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Figure 2— Photograph of the cervical spinal cord region of a dog, as seen at necropsy (lateral view; the c r a n i a l aspect is to the right and the caudal aspect is to the left of the photograph). Notice that the left nerve roots of spinal nerves C6 (white arrow) and C7 (dark arrow) are enlarged. A portion of the axillary mass (star) is evident at the distal aspect of the nerve root of spinal nerve C6. The mass invaded the spinal cord at this level (arrowhead).

✮

Figure 1—Photograph of a mass in the left axillary region of a dog (white arrows), as seen at necropsy. The left forelimb (black arrows) is abducted from the body, with the cranial aspect to the right and the caudal aspect to the left of the photograph.

locally invasive in peripheral locations or more highly invasive in locations close to the spinal cord.1,3,6 Point mutations of the neu oncogene have been detected in certain malignant peripheral nerve sheath tumors in dogs, cats, and horses.7 Time from onset of clinical signs until diagnosis of peripheral nerve sheath tumors ranges from 3 weeks to 3 years.1, 7-9 Excision or amputation of the limb may be curative if the mass is found early in the disease process.1,2,9 If involvement of the spinal cord is determined (by use of neurologic examination, myelography, or magnetic resonance imaging), laminectomy, excision or amputation, and radiation therapy may be attempted. Prognosis becomes much more grave when a nerve sheath tumor involves the spinal cord.1, 2, 10-12 In this dog, it seems likely that a “root signature” or the invasion of the brachial plexus by the mass was the initial cause of the lameness. Bailliere’s Comprehensive Veterinary Dictionary defines a root signature as “referred pain down a limb causing lameness or elevation of the limb, resulting from entrapment of a spinal nerve.”13 As the mass continued to grow, and entered the left side of the spinal cord, left hemiparesis developed. Extension of the mass into the vertebral canal compressed the spinal cord increasingly, causing tetraparesis. a

ACN Biopsy Needle, Medical Device Technologies Inc, Gainsville, Fla.

References 1. Brehm DM, Vite CH, Steinberg HS, et al. A retrospective evaluation of 51 cases of peripheral nerve sheath tumors in the dog. J Am Anim Hosp Assoc 1995;3:349–359. 2. Jones BR, Alley MR, Johnstone AC, et al. Nerve sheath tumors in the dog and cat. New Zeal Vet J 1995;43:190–196. 3. Targett MP, Dyce J, Houlton JEF. Tumors involving the nerve sheath of the forelimb in dogs. J Small Animal Pract 1993;34:221–225. 4. Hendrick M, Mahaffey EA, Moore FM, et al. Histological classification of mesenchymal tumors of the skin and soft tissues of domestic animals. In: The WHO international histological classification of tumors in domestic animals. 2nd series, vol 2. Washington, DC: Armed Forces Institute of Pathology, 1999;1–64. 5. Koestner A, Bilzer T, Schulman FY, et al. Histological classification of tumors of the nervous system of domestic animals. In: The WHO international histological classification of tumors in domestic animals, 2nd series, vol 5. Washington, DC: Armed Forces Institute of Pathology, 1999;1–71. 6. Kuntz CA, Dernell WS, Powers BE, et al. Prognostic factors for surgical treatment of soft-tissue sarcomas in dogs: 75 cases (1986–1996). J Am Vet Med Assoc 1997;211:1147–1151. 7. Stoica G, Tasca SI, Kim HT. Point mutations of neu oncogene in animal peripheral nerve sheath tumors. Vet Pathol 2001;38:679–688. 8. Stafuss AC, Martin CE, Baluch B, et al. Schwannoma in a dog. J Am Vet Med Assoc 1973;163:245–247. 9. Bradley RL, Withrow SJ, Snyder SP. Nerve sheath tumors in the dog. J Am Anim Hosp Assoc 1982;18:915–921. 10. Targett MP, Dyce J, Houlton JEF. Tumors involving the nerve sheaths of the forelimb in dogs. J Small Animal Practice 1993;34:221–225. 11. Wheeler SD, Clayton Jones DG, Wright JA. The diagnosis of brachial plexus disorders in dogs: a review of twenty-two cases. J Small Animal Practice 1986;27:147–157. 12. Oliver JE, Budsberg S. What is your neurological diagnosis? J Am Vet Med Assoc 1993;203:1275–1277. 13. Blood DC, Studdert VP. Root signature. In: Bailliere’s comprehensive veterinary dictionary. London: Bailliere Tindall, 1993;801. This report was submitted by Robert J. Vasilopulos, DVM; Andrew J. Mackin, BVMS, DVSc, DACVIM; David Jennings, DVM, PhD; and Robert Read, DVM, PhD; from the Departments of Small Animal Internal Medicine (Vasilopulos, Mackin), Neurology and Physiology (Jennings), and Pathobiology and Population Medicine (Read), College of Veterinary Medicine, Mississippi State University, Mississippi State, MS 39762-6100. Address correspondence to Dr. Vasilopulos. This feature is sponsored by the American College of Veterinary Internal Medicine on behalf of the specialty of neurology. Contributors to this feature should contact Dr. Helen L. Simons (800-248-2862, ext 6692) for case submission forms. Completed forms will be sent to Dr. Stephen Simpson at Auburn University for his review.

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