Feline Cauda Equina Syndrome Study Guide

Overview and Clinical Importance

Cauda equina syndrome (CES) refers to the clinical signs resulting from compression or damage to the bundle of nerve roots (the cauda equina) located caudal to the termination of the spinal cord. In cats, the spinal cord terminates at approximately the L7 vertebral level, which is more caudal than in dogs. The cauda equina consists of the L7, S1-S3, and caudal (Cd1-Cd5) nerve roots that travel through the lumbosacral vertebral canal before exiting through their respective intervertebral foramina.

While cauda equina syndrome is relatively rare in cats compared to dogs, it represents an important differential diagnosis for cats presenting with hindlimb weakness, lumbosacral pain, urinary or fecal incontinence, and tail dysfunction. The condition may result from degenerative lumbosacral stenosis (DLSS), trauma, neoplasia, discospondylitis, or congenital malformations such as those seen in Manx cats.

Anatomy of the Feline Lumbosacral Region

Vertebral Column

The feline vertebral column consists of seven cervical (C1-C7), thirteen thoracic (T1-T13), seven lumbar (L1-L7), three fused sacral (S1-S3), and a variable number of coccygeal vertebrae. The lumbosacral junction (L7-S1) is a critical anatomical landmark where degenerative changes most commonly occur. Unlike dogs, the feline vertebral bodies are more rectangular and elongated, with thinner, more tapered spinous processes.

Spinal Cord Termination

A key species difference is that the feline spinal cord extends more caudally than in dogs, terminating at approximately the L7 vertebral level (compared to L6 in large-breed dogs). The dura mater extends to approximately L7-S2 in cats. This more caudal position means that the conus medullaris itself may be affected by L7-S1 pathology in cats, potentially resulting in more severe neurological deficits compared to dogs with similar lesions.

Cauda Equina Nerve Roots

The cauda equina comprises the following nerve roots with their clinical functions:

Etiology and Pathophysiology

Degenerative Lumbosacral Stenosis (DLSS)

DLSS is the most common acquired cause of cauda equina syndrome in cats, though it occurs less frequently than in dogs. The pathophysiology involves Hansen Type II disc degeneration with subsequent protrusion into the vertebral canal, hypertrophy of the ligamentum flavum (interarcuate ligament), osteophyte formation on articular facets, and spondylosis deformans. Lumbosacral transitional vertebrae (LTV) are found in approximately 54% of cats with DLSS (compared to 16% of dogs), suggesting a stronger association in the feline species (odds ratio 18.5).

Traumatic Causes

Sacrocaudal luxation (tail-pull injury) is the most common spinal trauma in cats and results from traction on the S1-S3 nerve roots. This typically spares hindlimb function but causes variable disruption of bladder, bowel, and tail function. Lumbosacral fractures/luxations from motor vehicle accidents or falls can also cause acute cauda equina syndrome.

Congenital Causes: Manx Syndrome

Sacrocaudal dysgenesis (Manx syndrome) is an autosomal dominant condition in Manx cats causing varying degrees of sacral and caudal vertebral agenesis/dysgenesis. Affected cats may have spina bifida, myelodysplasia, meningocele, or absence of the cauda equina. Clinical signs include taillessness, bunny-hopping gait, plantigrade stance, urinary and fecal incontinence, and megacolon. Signs are typically present from birth and may be static or progressive.

Other Causes

Clinical Signs and Presentation

Clinical signs of feline cauda equina syndrome are typically lower motor neuron (LMN) in nature due to the peripheral nerve involvement. Signs may be acute or chronic and progressive, depending on the underlying etiology.

Common Clinical Signs

Neurological Examination Findings

On neurological examination, expect to find LMN signs affecting the pelvic limbs and tail. The patellar reflex may appear hyperreflexic due to loss of antagonism from the flexor muscle group (pseudo-hyperreflexia). The flexor (withdrawal) reflex, cranial tibial reflex, and gastrocnemius reflex are typically hyporeflexic or absent. Decreased perineal reflex and anal tone indicate S1-S3 involvement.

Diagnostic Approach

Initial Workup

The diagnostic approach begins with a thorough history and neurological examination to localize the lesion to the L4-S3 or cauda equina region. Routine laboratory tests (CBC, serum biochemistry, urinalysis) are typically normal unless concurrent disease is present. Urine culture should be performed if discospondylitis is suspected.

Diagnostic Imaging

Radiographic Findings in DLSS

• Narrowing of L7-S1 intervertebral disc space
• Sclerosis of L7 and S1 endplates
• Spondylosis deformans (ventral osteophytes)
• Spondylolisthesis (ventral displacement of S1 relative to L7)
• Lumbosacral transitional vertebrae (if present)

Differential Diagnosis

Treatment

Conservative (Medical) Management

Conservative management is appropriate for cats with mild pain as the only clinical sign, or when owners decline surgery. It involves strict rest (cage confinement for 4-6 weeks), weight management, and multimodal analgesia.

Surgical Management

Surgical intervention is indicated for failure of conservative management, severe or progressive neurological deficits, or urinary/fecal incontinence. Surgical options include: Dorsal laminectomy (decompression of vertebral canal), foraminotomy (enlargement of intervertebral foramen for nerve root decompression), discectomy/fenestration (removal of disc material), and lumbosacral stabilization (pins/PMMA or screws for instability).

Supportive Care

• Bladder management: Manual expression 3-4 times daily if atonic bladder; monitor for urinary tract infections
• Bowel management: Stool softeners (lactulose); dietary fiber; enemas if obstipated
• Physical rehabilitation: Passive range of motion; hydrotherapy; controlled exercise
• Environmental modification: Low-entry litter boxes; ramps; soft bedding

Prognosis