Neurologic lesion localization: Spinal neuropathies (Proceedings)

Spinal cord localization principles

It is helpful to develop an ordered approach to this problem. The following stages in the diagnostic approach should include:

1. Identifying the problem

2. Localizing the lesion

3. Assessing the severity or extent of the lesion

4. Acquiring a diagnosis

5. Determining the prognosis

Identifying the problem

History

1. Age/Breed

2. Previous history of illness; recent or previous trauma.

3. Course of the clinical signs –

Onset – very obvious or vague?

What were the initial signs? Any asymmetry?

Acute vs. progressive vs. static

Has condition stabilized, improved, worsened?

Has problem occurred before?

Clinical Examination:

It is important to do a thorough physical exam so that other diseases which may mimic neurologic conditions are not overlooked. Especially orthopedic disorders

Localization of the lesion

Determine the locomotor status first; this will help one evaluate which limbs are involved and assess for asymmetry, strength, and ataxia.

Assessment of proprioception

1. Knuckling response

2. Reflex stepping

3. Wheelbarrowing

4. Lateral hopping

Myotatic reflexes

Muscle atrophy –

1. LMN – severe, within 7-10 days

2. UMN – mild, takes weeks to occur

Other reflexes that may be evaluated –

1. Cutaneous trunci reflex –

Afferent arm – segmental sensory nerves

Efferent arm – C8-T1 – lateral thoracic nerve

2. Withdrawal reflexes –

Front limb – C5-T1 cord segments

Hind limb – L6-S1 cord segments

3. Anal reflex – S1-S3 cord segments

4. Crossed extensor reflex – this is manifested as a very rapid and extreme flexion of the stimulated limb after a noxious stimulus, with simultaneous extreme rapid extension of the opposite limb.

Bladder function

1. S1-S3 cord segments supply LMN and motor control to the bladder wall and urethral sphincters.

2. UMN vs. LMN bladder

a. UMN – 1. bladder may be full and distended

b. high resistance to manual compression

c. urine stream continues for a brief period after manual compression is stopped

d. after several days post-cord injury, the bladder will become hyperreflexic and hold less urine during the storage phase, but still retains more urine than a normal bladder after voiding.

e. LMN – 1. bladder full and distended

f. flaccid, no tone

g. dribbling of urine

h. bladder easy to express and urine stream ceases as soon as compression is stopped.

Horner's Syndrome

1. Sympathetic denervation to the eye resulting in ptosis, miosis, enophthalmus, protruding nictitans.

2. Lesions involving C8-T2 cord segments and/or nerve roots may results in Horner's Syndrome. Rarely may be seen with higher cervical cord lesions.

Cranial Nerve Examination

1. Should be evaluated briefly just to make sure that there is no evidence of multifocal or disseminated CNS disease.

Assessing the Severity of the Lesion

This is important since the prognosis for the patient may initially be based upon this assessment. Many times the severity of the lesion has as much bearing on the prognosis as the etiology.

1. In general, dogs with spinal disease which have LMN deficits have a worse prognosis for return of function than those with UMN deficits.

2. Degree of dysfunction can be graduated

a. I - pain

b. II - Ataxia with mild paresis

c. III - Non-ambulatory with voluntary movement

d. IV - Paraplegia

e. V - Paraplegia with loss of pain recognition

3. Evaluation of response to noxious stimuli

a. Presence of the withdrawal reflex does NOT indicate intact pain recognition.

b. Patient must respond to a noxious stimulus by biting, growling, crying out, etc. to support that animal has conscious pain recognition.

c. Is there a sensory band? Test both dorsal and ventral surfaces of the trunk.

4. Other findings that do not mean "functional cord transaction" but do point to severe cord injury

a. Crossed extensor reflex

b. Schiff-Sherrington sign

c. Lack of cutaneous trunci reflex caudal to cord lesion, with return of the reflex cranial to the lesion.

Localization of Lesions Based Upon Spinal Cord Syndromes

Sacrococcygeal syndrome (Cord Segments S1-S3 thru caudal nerves)

1. May see some very mild paresis of rear limbs, but animal is still ambulatory and able to support weight

2. Flaccid weakness (paresis to paralysis) of tail

3. LMN bladder with overflow incontinence

4. Dilated anus, depressed to absent anal reflex

5. Fecal incontinence

6. ± pain at lumbosacral junction.

Common causes of the sacrococcygeal syndrome in practice –

1. Pelvic fractures and luxations, vertebral fractures L5-L7

2. Sacrococcygeal separation, esp. in cats

3. Degenerative disc disease

4. Discospondylitis

5. Lumbosacral instability in large breeds

6. Fibrocartilagenous emboli

7. Sacrococcygeal dysgenesis in Manx cats and English bulldogs

8. Neurofibromas

9. Bite wound abscesses in cats

10. Neoplasia of bone can be primary or metastatic, as in the case of prostatic neoplasia.

Lumbosacral Syndrome (Cord Segments L5-S1)

1. Flaccid paresis to paralysis of hind limbs

2. Depressed to absent postural test reactions in pelvic limbs

3. Reduced myotatic reflexes (patellar, gastrocnemius, withdrawal, anterior tibial)

4. Muscle atrophy, decreased muscle tone

5. Possible asymmetry if lesion more one-sided

6. *Note – all of those signs mentioned under sacrococcygeal syndrome could also be seen with these above signs if cord lesion is extensive enough.

Common causes of the Lumbosacral Syndrome in Practice

1. Lumbar vertebral fractures – L5-L7

2. Fibrocartilagenous emboli

3. Degenerative disc disease

4. Discospondylitis

5. Cord neoplasia

6. Vertebral neoplasia

7. Congenital vertebral malformations, myelodysplasias

Thoracolumbar Syndrome (Cord Segments T3-L4)

1. Spastic paresis/paralysis in pelvic limbs

2. Hyperreflexia of tendon reflexes in pelvic limbs

3. UMN bladder, spastic incontinence

4. If lesion is more one-sided could see asymmetry between pelvic limbs.

5. Depressed postural reactions in pelvic limbs

6. Ataxia in pelvic limbs

7. ± crossed extensor response in pelvic limbs

8. ± Schiff-Sherrington phenomenon

9. ± lack of panniculus reflex caudal to lesion

Common causes of Thoracolumbar Syndrome in Practice

All of those etiologies seen with lumbosacral syndrome plus the following:

1. Degenerative myelopathy (Ger. Sheps primarily)

2. Distemper myelitis

3. Myelomalacia

Cervicothoracic Syndrome (Cord Segments C6-T2)

1. Monoparesis/plegia, hemiparesis/plegia, tetraparesis/plegia

2. Depressed tendon reflexes to front limbs

3. Hyperreflexia of tendon reflexes in pelvic limbs

4. Postural tests diminished in all limbs, or just on one side

5. Urinary incontinence (spastic)

6. Depressed panniculus reflex (uni or bilateral)

7. Horner's Syndrome (uni or bilateral)

8. May see asymmetry if lesion is more one-sided

Common causes of Cervicothoracic Syndrome in Practice

1. Degenerative disc disease

2. Discospondylitis

3. Infectious causes of meningitis and myelitis

4. Granulomatous meningomyelitis (reticulosis)

5. Fractures, luxations of vertebrae

6. Brachial plexus avulsion

7. Wobbler Syndrome of the Doberman, and some other large breed dogs

8. Fibrocartilagenous emboli

Cervical Syndrome (Cord Segments C1-C5)

1. Spastic hemiparesis/plegia to tetraparesis/plegia

2. Hyperreflexia of all myotatic limb reflexes (front and rear)

3. Cervical pain, rigidity

4. Reduced flexion/extension of head, neck

5. Postural reactions depressed in all limbs

Common causes of Cervical Syndrome

Most all of those seen with Cervicothoracic Syndrome with the addition of:

1. Atlantoaxial problems in toy breeds

2. Suppurative steroid-responsive meningitis

3. Rickettsial meningitis – Ehrlichia

4. King Charles Cavalier Spaniel – caudal occipital malformation (syringomyelia or COMS)

Spinal conditions in which pain may be the major or only presenting sign

1. Cervical Pain

2. Disc protrusion – do not forget lateralizing discs in cervical foramina

3. Infectious meningitis-bacterial, fungal

4. Steroid responsive meningitis

5. Discospondylitis

6. Neoplasia – usually osseous

7. Atlantoaxial problems

8. Distemper – but rare

Thoracolumbar Pain

1. Disc disease

2. Discospondylitis

3. Osseous neoplasia

4. Extradural tumors, and sometimes intramedullary tumors

Low Lumbar Pain

1. Those seen with Thoracolumbar pain

2. Lumbosacral instability

3. Neoplasia – especially prostatic carcinoma metastasis