T. Flegel, DECVN, DACVIM (Neurology)
Department of Small Animal Medicine, University of Leipzig, Leipzig, Germany
Tail-pull injuries are seen secondary to road traffic accidents. It is thought that they develop if the cat's body is accelerated during the accident whereas the tail is trapped at the same time. In the context of this talk, we summarize coccygeal fractures and/or luxations as well as caudal sacral fractures under the term of a tail-pull injury, since all of those may cause similar clinical symptoms and may have therefore to be addressed in a similar way.
A tail-pull injury may be the only lesion following trauma, or it may be more commonly associated with other lesions of the skeletal system or with soft tissue trauma. Based on patients of our own hospital, the following lesions can be found in addition to tail-pull injuries: pelvic fracture/iliosacral luxations (46%), rear limb fractures (18%), additional spinal fractures (11%), pulmonary contusions (14%), pneumothorax (7%), craniofacial injuries (7%) as well other soft tissue injuries (14%), whereas in 21% of cats tail-pull injury is the only lesion. Therefore, a cat with a tail-pull injury should be critically evaluated for additional lesions by taking radiographs of at least the caudal axial and appendicular skeleton as well as of the chest. By the same token, every traumatized cat with rear limb or pelvic fractures should be carefully scrutinized for a tail-pull injury, since it may affect long-term prognosis of the patient more than other lesions.
Pure injuries to the coccygeal spinal segments should be causing sensory and motor deficits of the tail only. However, sacral and maybe even caudal lumbar spinal segments may be affected as well, since tail-pull injuries can cause significant traction to the nerve roots. Therefore, additional neurological deficits including different degrees of impaired rear limb motor function and micturition disorders are commonly seen.
Depending on the severity of traction, the following motor deficits based on affected spinal cord segments may be observed:
Obturator nerve (L4–6): Rear limb abduction
Femoral nerve (L4–6): Inability of stifle extension during weightbearing
Sciatic nerve (L6–S2): Dragging limb, inability to put weight on the limb
Pelvic nerve (S1–3): Flaccid tail
However, micturition disturbances caused by impaired innervation of the bladder detrusor muscle and the urethra can be more important for the cat's long-term prognosis, even though those lesions may appear less dramatic than pelvic or axial skeleton fractures on initial assessment.
Micturition is a complex interaction of both the sympathetic and parasympathetic nervous system. Sympathetic innervation of the bladder detrusor muscle via the hypogastric nerve (L1–5 in cats) allows urine storage by relaxing the bladder wall, whereas α-sympathetic innervation of the smooth muscle sphincter increases the sphincter tone during the storage phase. Voiding, however, is mainly achieved by activation of the parasympathetic system via the pelvic nerves (S1–3) which initiate detrusor muscle contraction. At the same time α-sympathetic inhibition and voluntary external striated sphincter muscle relaxation via pudendal nerves (S1–3) allow bladder emptying. All those processes are controlled by higher centers in the brainstem and the cerebrum.
One would assume that a lesion affecting the spinal nerves S1–3 as it is the case in sacrococcygeal injury would almost exclusively cause a flaccid detrusor muscle and a relaxed sphincter, which would allow for easy manual bladder expression. However, in some cases cats have difficulties emptying the bladder due to increased sphincter tone. This is explained by additional traction injury to the lumbar spinal cord segments during the traumatic event.
There is a good correlation between urinary and fecal incontinence. Therefore, reduced anal sphincter tone may indicate risk of urinary incontinence.
In cases where micturition disorders following a sacrococcygeal injury develop, prognosis for recovering normal micturition largely depends on the localization and type of lesion. Functional recovery in cases where the sacral spinal nerves have been injured depends on the type of neuronal pathology. In cats with complete severance of the nerves (neurotmesis) that supply the bladder sphincter mechanism and detrusor muscle, the prognosis for recovery of normal bladder function is hopeless. In contrast, cats who suffer from neurapraxia (temporary functional loss without structural lesion) will recover, and those suffering from axonotmesis (transection of the axon, but intact nerve sheath) may recover.
However, in affected cats it might not be possible to determine the type of lesion according to the classification explained above, and therefore the prognosis is difficult to determine. However, it is known that most cats that recover normal micturition will do so usually within 30 days.1 Existence of deep pain sensation 5 cm distal of the tail base may predict outcome shortly after the trauma.2 All cats with intact deep pain sensation within the first 48 hours following sacrococcygeal trauma did recover spontaneous micturition within 3 days. In contrast, 36% of all cats without deep pain sensation at the tail base did not recover urination within 30 days. Therefore, tail base deep pain sensation may be used as a prognostic indicator.
Electrodiagnostic examination of the coccygeal nerves would be another tool to determine prognosis for recovery of normal micturition early following trauma. A positive response of the tail muscles does indicate survival of at least some motor fibers. The assumption would be then, that the same may apply to fibers of the autonomic nervous system supplying the bladder detrusor as well as the urethral and anal sphincter muscles.
Therapeutic options included medical therapy and different surgical approaches. As explained above, micturition abnormalities may vary, but in many cases the bladder cannot be emptied due to decreased detrusor tone and/or due to increased urethral sphincter tone. Both abnormalities can be addressed medically.
Medication to increase bladder detrusor muscle tone: bethanechol (cholinergic): 1.25–7.5 mg/cat BID (twice daily) to TID (three times daily). Medication to decrease urethral sphincter tone: alfuzosin (α1-blocker): 2.5 mg/cat SID (once daily), phenoxybenzamine (non-selective α-blocker): 2.5–7.5 mg/cat BID, prazosin (α1-blocker): 0.25–0.5 mg/cat SID to BID, acepromazine 0.2 mg/cat BID; diazepam (striated muscle relaxant): 1–2.5 mg/cat TID, dantrolene (striated muscle relaxant): 0.5–2 mg/cat TID.
Medication strengthening bladder detrusor muscle tone should only be used in cats that can be easily expressed due to a low sphincter tone. Otherwise, the bladder wall may contract against a closed sphincter, causing additional stress to the bladder wall. The latter may result in a poor long-term prognosis for functional recovery of normal micturition. Initially, medical therapy may be combined with either of the following methods for bladder emptying depending on the urinary sphincter tone: manual expression, intermittent catheterization, and permanent indwelling catheter placement.
Surgical treatment is addressing two objectives. On one hand, it has to be decided if a sacral fracture has to be treated and if the tail is preserved or amputated. On the other hand, surgical options may help to facilitate bladder emptying.
Sacral and sacrococcygeal fractures should be treated surgically if there is a significant narrowing of the spinal canal or if the cat is in severe pain, indicating nerve root compression that does not respond to pain medication. There is an ongoing debate about stabilizing sacrococcygeal fractures/luxations or amputating the tail. There are two arguments for tail amputation. First, a completely paralyzed tail is of no use for the cat. It may be soiled during urination and defecation, causing secondary skin reactions. Secondly, it is believed that a paralyzed tail may apply continuous traction due to its weight to the sacral and lumbar spinal cord segments if there are still a few intact nerve sheaths. This continuous traction may cause additional injury to the spinal cord. If that is truly the case, it has never been proven. We tend to amputate the tail if there is a fracture/luxation with a large gap, assuming that no nerves have survived such traction, whereas we attempt fracture/luxation repair of the first two coccygeal segments with a small gap. Surgical options for bladder management include placing a cystotomy tube and sphincterotomy for widening of the functional urethral sphincter muscle in cases of increased sphincter tone.3
1. Smeak DD, Olmstead ML. Fracture/luxations of the sacrococcygeal area in the cat: a retrospective study of 51 cases. Vet Surg. 1985;14:319–324.
2. Tatton B, Jeffery N, Holmes M. Predicting recovery of urination control in cats after sacrocaudal injury: a prospective study. J Small Anim Pract. 2009;50:593–596.
3. Grevel V, Jurina K. Sphinkteromomie des Blasenhalses zur Therapie der Reflex-Dyssynergie nach Rückenmarksverletzung bei drei Katzen. Kleintierpraxis. 1994;39:529–538.