Ataxia in cats
| Causes | |
| Trauma | |
| Intervertebral disc disease | Sacrococcygeal fractures |
| Vascular compromise | Neoplasia |
| Subarachnoid cysts | Syringomyelia |
| Inflammatory disease | Infectious disease |
| Vestibular disorders | Hypervitaminosis A |
General aspects of Nervous dysfunction
Lower motor neuron (LMN) damage results in loss of resting muscle tone, myotactic reflex, voluntary movement and disruption of tendon reflex arc resulting in hypotonia, hyporeflexia and atrophy (rapid, profound and specific)
Upper motor neurons (UMN) cross over close to their origins in the reticulospinal and rubrospinal tracts. Therefore lesions below these areas give ipsilateral signs. Reflexes are usually enhanced, resulting in paresis, hyperreflexia (clonus), spasticity/hypertonia and occasionally abnormal reflexes.
Clinical signs related to anatomic localisation
| Anatomical site | Concomitant signs |
| C1-C5 | Not common site for lesions in the cat: neck pain, ataxia and proprioceptive deficits in pelvic +/- thoracic limbs, increased/normal spinal reflexes and muscle tone all limbs (UMN) |
| C6-T2 | Thoracic limb lameness, ataxia and proprioceptive deficits in pelvic +/- thoracic limbs, paresis/plegia in all/some limbs, decreased spinal reflexes and muscle tone in thoracic limbs (LMN), increased/normal spinal reflexes and muscle tone in pelvic limbs (UMN), UMN ipsilateral to forelimbs, ipsilateral signs |
| T3-L3 | Thoracolumbar pain, ataxia and proprioceptive deficits in pelvic limbs, paresis/plegia in pelvic limbs, normal spinal reflexes and muscle tone in pelvic limbs, increased/normal spinal reflexes and muscle tone in pelvic limbs (UMN) |
| L4-S3 | Lumbar/sacral pain, ataxia and proprioceptive deficits in pelvic limbs, pareses/plegia in pelvic limbs, normal spinal reflexes and muscle tone in thoracic limbs, decreased spinal reflexes and muscle tone in pelvic limbs (LMN) |
High dose methylprednisolone sodium succinate is best administered within 8 hrs of injury. Dosages of 30mg/kg IV as an initial bolus dose are fairly standard.
2. Sacrococcygeal fractures
Tail pull injuries are very common. There is still debate about the need to amputate the tail even in mild cases. The reason for amputation include immediate improvement in analgesia and a reduction in traction to the spinal cord from a flaccid non-functional tail. No data yet to support these hypotheses.
| Clinical signs and prognostic indicators in sacrococcygeal injuries | ||
| Caudal segments/nerve root | Flaccid analgesic tail, normal urination and defecation | 75% regain tail function |
| Caudal segments/nerve root and pelvic nerves | Flaccid, analgesic tail, postures to urinate, inability to void urine, easy to express bladder, normal defecation | 75% regain tail function and most regain urinary function in 2-4 weeks |
| Caudal segments/nerve root | Flaccid, analgesic tail, decreased anal tone and reflexes, absence of posturing to urinate, difficult to express bladder (pudendal nerve reflex dysnergia) | Some regain urinary function over the next 1-2 months |
| Caudal segments/nerve root | Flaccid, analgesic tail, absent anal tone and reflexes, absent of posturing to urinate, faecal incontinence, easy to express bladder | 25% regain urinary function within 2-3 months |
Bladder function can be divided into 2 categories:
1. If the bladder is easy to express and overflows when full, the lesion is likely to be located at spinal cord segments S1-S3 as the pudendal nerve originates from these segments and innervates the detrusor muscle and the skeletal muscle of the urethra. Thus, damage here results in flaccid paralysis of these muscles. This is the so-called lower motor neurone bladder. Classically, cats with tail pull injuries manifest like this. Anal tone and sensation will also be absent or reduced as this area is also innervated by the pudendal nerve. Urine usually gushes out of these cats when they are picked up. Chronically, these bladders can be more difficulty to express. This may be a result of continued and perhaps increased sympathetic stimulation of the urethral smooth muscle. This derives from the hypogastric nerve which originates from L2-L5 in cats.
2. If the bladder is difficult to express and does not overflow (or overflows only if the bladder is really distended) the lesion is likely to be located between T3-L3 (assuming the forelimbs are normal). A lesion here results in spastic paralysis of the bladder, the classic upper motor neurone bladder, because of the same loss of upper motor neurone pathways that affect the limbs. If an UMN bladder overfills, the tight junctions between the detrusor muscle can be irreparably damaged so that the bladder function will never be regained and bladder tone will decrease. In general, the UMN bladder will regain function at the same time abd at the same rate as the limbs. However, the behavioural attributes of cats may influence whether this truly happens in practise. Cats being fastidious creatures will often not voluntarily urinate unless they can get themselves into the litter box and at the very least posture relatively normally.
3. Infectious disease
Infectious agents include bacteria, virus (FIP), fungi (Cryptococcus and other fungi), protozoa (Toxoplasma). Viral meningitis in cats is most commonly caused by FIP, followed by Cryptococcus. A high suspicion of FIP is made on age, signalment, and supporting laboratory data.