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Review Article: When to Refer Spinal Cases?

Ideally, any animal showing signs indicative of spinal pain and/ or neurological deficits should undergo thorough investigation to achieve a definitive diagnosis: Only then can an accurate prognosis be offered and rational advice be given.  E.g.: non-surgical management of thoracolumbar disc disease (six weeks cage-rest) differs markedly from the management of ischemic myelopathy, or FCE where no underlying disc disease has been found (early active physiotherapy). However, the two conditions above present with very similar signs which cannot initally be distinguished on the basis of clinical findings alone.

Sagittal T1W MR-scan of Hansen type II disc deformation to compress overlying spinal cord.

The decision to opt for surgical therapy is based primarily on the severity of the spinal lesion. For a suspected thoracolumbar disc problem it is helpful to grade each case as below, as this may indicate the necessity for early referral and the likelihood of a successful outcome.

Grade I – spinal pain; no neurological deficits

Grade II – conscious proprioceptive deficits with paresis or ataxia of one or more limbs, but patient remains ambulatory

Grade III – patient unable to stand or walk but retains urinary control

Grade IV – loss of urinary control (either flaccid incontinence or overflow)

Grade V – loss of conscious pain perception (aka deep pain sensation’) caudal to the lesion*

* – deep pain sensation should initially be assessed by squeezing the toes with a pair of artery forceps, until the animal shows distress by vocalising or turning towards the painful stimulus. If the leg is withdrawn it is merely a demonstration that the local reflex arc is intact – seen even in cases where the cord has been completely transected. Should no conscious reaction be seen, progress to using a pair of heavy-duty bone-holding forceps higher up the limb to firmly grasp a long bone. It is possible to detect deep pain sensation in a significant number of cases that have shown no reaction to having the toes pinched.

Prognosis:

Patients graded I-II are often managed conservatively in the first instance, unless signs are recurrent or non-responsive.  Those grade III+IV have a good prognosis (95%+ return to walking within three months) with decompressive surgery.  Those graded V require emergency decompression within 48hours, when approximately 60% will return to walking.  Note: cases graded V after tramua, e.g. RTA are extremely unlikely to regain suffcient function to walk, or voluntary bladder control.

In addition, it useful to is assess whether limb deficits are upper or lower motor neurone in character:

Signs UMN LMN
Limb muscle tone Increased Decreased
Spinal reflexes (e.g. patella/ withdrawal/ perineal) Increased Decreased
Urinary Incontinence Very full bladder – difficult to express Bladder feels flaccid and is easily expressible

Irrespective of the grade or cause of the spinal lesion, animals with upper motor neurone signs have a  better chance of a rapid return to normal/ near normal function as compared to those with lower motor neurone signs.