Downs Veterinary Referrals

Goals of Assessment

What questions should your assessment be able to answer?

An owner might be expected to inquire:

• what is wrong with their pet?
• what are the various treatment options?
• what do these options entail, in terms of morbidity, risks, length and extent of rehabilitation, costs and (in the case of referral) travel involved?
• is it going to recover sufficiently to ensure an adequate quality of life for a significant length of time?

We can best answer the above by addressing the following questions:

• Does the patient actually have spinal problem?
• How urgently do I need answers so as not to affect the outcome adversely?
• What is the prognosis based on the  history and initial clinical findings – including grading and localisation of any spinal cord lesion?
• Which tests should be run first?

Is there a primary spinal lesion?

The presence of disease out with the CNS may mimic signs of neurological impairment (ataxia, paresis, plegia or pain).  Other body systems should always be critically assessed as part of the initial examination:

Orthopaedic disease.

Check for signs of bilateral cruciate/ hip problems or polyarthritis.  Rarely, conditions  involving the bone marrow (e.g.  multiple myeloma/ inflammatory disease) can also confuse the clinical picture.

Shock.

In trauma cases, neurological assessment can be complicated by reduced reflexes and altered conscious pain perception (CPP aka ‘deep pain sensation’) of external stimuli, especially when potent, opioid analgesics have been used to stabilise the patient.  It is therefore essential to repeat the neurological assessment once shock has been treated.

Cardiac/ circulatory disease.

Is there evidence of circulatory failure or thromboembolic disease that might explain the patient’s signs?

Portosystemic shunts may present with ataxia – bile acid stimulation testing might be considered where no surgical spinal lesions are found.

Other metabolic disease.

A basic blood panel including electrolyte screening should ideally be run on site to rule out Addison’s disease or other endocrine/ renal/  hepatic disorders.

Neuromuscular problems.

Consider distal denervating disease (aka polyradiculoneuritis), myositis, myasthenia gravis, botulism and tetanus if neurolocalisation fails to identify a spinal lesion.

Abdominal, intrapelvic or retroperitoneal pain.

Spinal disease often presents as intermittent or low grade discomfort.  It may be confusing where the locus of pain is poorly localised or referred from elsewhere.  Therefore, it is important to rule out extra-spinal pathology such as pancreatic, prostate or renal disease.

Intracranial/ behavioural.

Spinal conditions often result in altered behavioural patterns as a consequence of pain or altered function; it may be worth considering a brain or primary behavioural problem if clinical findings do not support the presence of spinal cord disease.

Table of Common Spinal Disease Differentials and their Typical Presentation

Based on signalment and history alone, the probability of  one or other disease process being present may determine the order in which further tests are performed, particularly where funds are scarce.  Despite this, it should be noted that  no single set of presenting signs can be considered pathognomonic for any given differential:  i.e. for each clinical picture, the differential list cannot be narrowed to a single diagnosis without recourse to further investigations.

Grading cord injury

Why do we grade spinal cord lesions? Firstly, to offer an initial prognosis and secondly, to monitor clinical progress, both in patients managed conservatively and following surgery; the manner in which a case is managed may fundamentally alter, depending on the results of repeat grade assessment.

In terms of the prognosis, the single most useful clinical finding is the presence or absence of CPP:- At first presentation, if there is no evidence of CPP the prognosis for a return to walking changes significantly from good to poor (at best),  irrespective of the inciting cause.

For example, CPP-negative trauma cases can be offered euthanasia after reversal of any shock as these are extremely unlikely torecover cord function sufficiently to enable a return to walking/ urinary continence.

Conversely, the presence of CPP indicates further assessment and appropriate management will prove worthwhile in most cases as long as the cause of the lesion can be  stabilised and effectively treated.

Specifically, with suspected disc disease, loss of CPP is an indication for urgent advanced neuroimaging as appropriate decompression must be performed within 48 hours to give a 50-60% chance of a return to walking.  Any surgery performed after this window has a much reduced success rate.

The continued presence of CPP in patients with confirmed disc disease suggests a 90% chance of a return to walking with appropriate management.

By definition, CPP-negative patients must have a lesion caudal to Ce7 as otherwise, respiratory paralysis would result.

fig.1 - testing for conscious pain perception is an integral part of the initial assessment of spinal patients; point-pressure on the periosteum is sometimes needed to elicit a response.

How to check for CPP

A simple toe-pinch should incite a conscious response from the patient; they may vocalise, turn their head towards the area being stimulated or at the very least, change their breathing pattern consistently.

Withdrawal of the pes and/ or tail movement without a higher, conscious response does not indicate the presence of CPP, but merely indicates that the local reflex arc is intact.

Should the patient not respond as above to a digital toe-pinch, artery forceps may be tried, progressing to point pressure on the periosteum (e.g. with a pair of bone-holding forceps – see fig. 1) to check for evidence of CPP.

Patients may display very subtle signs of CPP, but recognition of any higher response at all is critical to being able to offer an accurate prognosis.  The importance of repeat assessments in this regard cannot be overstated, in terms of arriving at a definitive opinion.

Lesion Localisation

Why is it important to localise the lesion?

Obviously, it helps expedite imaging to narrow the region of the spine affected. Moreover, a specific location, in conjunction with the history, signalment and other clinical findings, may help to order the various differentials according to probability.  For instance, a mature Dachshund that presents with peracute paraplegia and the lesion localises to the T3-L3 cord segments, is more likely to be suffering from a compressive disc extrusion than a five-month-old Lurcher with spinal pain, but no deficits or history of trauma, and a diffuse/ multifocal localisation.  Also, in our experience, upper motor neurone (UMN) lesions recover more rapidly and with fewer residual deficits than lower motor neurone (LMN) insults, so neurolocalisation can also influence the initial prognosis.

Which Test Should I Run First?

Where the history, signalment and clinical findings are consistent with a spinal cord lesion, the next investigative step will depend on several factors, including the financial resources and the diagnostic facilities that are available, as well as the expectations and wishes of the owner.

However, some form of imaging will be an essential part of any further work-up.

Radiology is commonly performed for assessment of spinal disease.  However, the diagnostic yield is often low.  In addition, abolishing the paraspinal muscle splinting effect by anaesthetising and then positioning a compromised spine can instead make matters worse.

fig.2 - lateral radiograph of 8-week old Cocker Spaniel (see link below for case report) presenting three days after colliding with a stair-gate; there is significant malalignment of the neural canal.

Conscious (and therefore potentially, sub-optimal) views of the spine should be considered in trauma cases where gross disruption to the integrity of the spine will dictate the immediate treatment plan; these can be obtained once the patient has been stabilised (see fig. 2).

This scenario contrasts with those cases that have a high probability of disc-related pathology; where funds are tight, it may be preferable to arrange advanced imaging in the first instance, rather than incur costs for radiograph that are likely to be inconclusive.  Even with neoplastic lesions, changes seen on plain radiographs (if any) are often subtle and most will still require further imaging for an accurate prognosis to be given.

Cerebrospinal fluid (CSF) analysis is another test traditionally offered as an integral part of any neurological assessment.  Again, the diagnostic yield for this procedure is low with spinal pathology.  Where inflammatory CNS disease is suspected, the additional risk of brain-stem herniation at CSF collection must be born in mind.  MRI assessment to identify raised intracranial pressure prior to spinal taps greatly reduces this risk.

Related case report

Cervical Fracture in an eight-week-old Cocker Spaniel.

Summary

Spinal patients can be challenging to assess given that the initial presenting signs can be vague, intermittent, referred or poorly localised, particularly in cases where nerve-roots are involved.  The diverse and dynamic nature of underlying pathology may also give rise to a variable and unpredictable clinical progression.  In addition, many cases require advanced diagnostic techniques to achieve a definitive diagnosis.

Timely recognition of unstable patients – both medical and surgical – coupled with a logical plan for further investigation, will maximise the chances of a rapid resolution of spinal pain and restoration of cord function where possible.

Just as importantly, for those cases with a guarded prognosis, the above approach will keep morbidity to a minimum.