Degenerative Lumbosacral Stenosis (DLSS)
Background
The lumbosacral region is where the last lumbar vertebra (L7) meets the sacrum (of the pelvis). In addition to bone, it includes connective tissues such as the articular joints, ligaments, and the intervertebral disc. At this level, the spinal cord has ended, and a bundle of spinal nerves called the cauda equina (named for its ‘horse tail’ appearance) continues through the canal. These nerves branch out to exit the vertebrae to innervate the hind limbs.
Diagram of the lumbosacral vertebrae, ligaments, spinal cord, and meninges. (Courtesy of L. Campoy, LV, CertVA, Dip ECVAA, MRCVS, Ithaca, NY and Cornell University, Ithaca, NY.)
What is DLSS?
DLSS (also known as lumbosacral disease or cauda equina syndrome) is a degenerative, multifactorial condition of the lumbosacral junction leads to compression of the cauda equina.
Pathology changes commonly seen in dogs with DLSS include:
- Thickening of the ligaments stabilising the joint
- Protrusion of disc into the canal
- Degenerative joint changes to articular joints
- Dynamic compression of the cauda equina
- Dynamic narrowing of intervertebral foramen
- Congenital narrowing of the vertebral canal
- Sacral osteochondrosis
Diagram of protruding disc at lumbosacral joint.
(From Sjöström L: Degenerative lumbosacral stenosis: surgical decompression. In Slatter DH, editor: Textbook of small animal surgery, ed 3, Philadelphia, 2003, Saunders/Elsevier
What are the clinical signs of lumbosacral disease?
Lumbosacral disease most commonly affects mature, large-breed dogs (e.g., German Shepherd) due to age-related degeneration structures around the lumbosacral spinal canal.
Clinical signs depend on the severity and duration of the condition and are often related to inflammation or compression of the LS nerves. Signs may include:
• Pain on palpation of the lumbosacral region (lower back)
• Unilateral or bilateral pelvic limb lameness or weakness
• Hindlimb incoordination (ataxia)
• Difficulty jumping or ascending stairs
• Slow to rise from a lying position
• Abnormal posture or tail carriage
• Urinary or faecal incontinence
• Pain on a “tail-jack” test
• Muscle loss (atrophy)
How is lumbosacral disease diagnosed?
Investigation begins with a clinical history, followed by a physical and neurological examination looking for findings consistent with the clinical signs described above. If DLSS is suspected, advanced imaging of the lumbosacral region is recommended.
This typically includes MRI (magnetic resonance imaging), which is considered the best imaging modality for diagnosing DLSS. MRI provides detailed images of the spinal nerves, intervertebral disc and surrounding soft tissues allowing identification of inflammation and compression of the cauda equina. CT (computed tomography) may also be performed, particularly to better assess the bones of the lower spine or to assist with surgical planning.
Additional tests may occasionally be recommended. These can include collection of cerebrospinal fluid (a spinal tap) to assess for inflammation or rule out infectious or inflammatory diseases, and electrodiagnostic testing, which evaluates the function of the specific nerves leaving the spinal canal.
MRI showing on the left shows a dog with DLSS with the red arrow pointing towards a degenerated disc protruding into the spinal canal.
What treatment options are available?
Treatment of lumbosacral disease involves either conservative medical treatment or surgical intervention depending on the duration and severity of the clinical signs. Your veterinarian will recommend the most appropriate treatment based on your pet’s individual condition.
Conservative management
Dogs with mild disease often respond well to medical management and may return to normal pain-free mobility with some eventually able to discontinue medications. However, recurrence of clinical signs can occur.
Conservative management includes:
• Strict rest and exercise restriction – confinement to a crate, fenced off area in backyard or small room (avoiding stairs and jumping on/off furniture). Dogs should be taken outside on a lead for toileting only.
• Weight management if overweight, to reduce stress on the lumbosacral spine.
• Physiotherapy to support strength and mobility during recovery.
• Anti-inflammatory drugs (e.g. meloxicam) to reduce pain and inflammation
• Additional pain-relief (e.g. gabapentin)
Epidural steroid injections
If conservative management is unsuccessful, epidural steroid injections may be considered prior to surgical intervention to provide longer-term pain relief. Previous studies reported an improvement in approximately 80% of dogs. Some protocols recommend a series of three injections, administered at day 1, 2 weeks and 6 weeks. Repeated injections may be considered every 6 months thereafter.
However, not all dogs respond adequately to medical management or epidural injections. In some cases, pain may persist or gradually worsen as the condition progresses. If this occurs, or if neurological signs such as weakness or difficulty walking develop, surgical treatment may be recommended to relieve pressure on the affected nerves.
Surgical intervention
The goal of surgery is to relieve pressure on the nerves at the LS region, which can improve comfort, mobility, and overall quality of life. In many cases, surgery provides good long-term results such as reduced pain and improved neurological function.
The exact procedure depends on the findings from advanced imaging. Surgery typically involves one or more of the following:
• Dorsal laminectomy – a procedure that removes a small portion of bone from the top of the affected vertebrae (L7-S1) to relieve pressure on the nerves
• Foraminotomy – widening the opening where the spinal nerves exit the spine
• LS stabilisation – in some dogs, implants may be used to stabilise the joint and reduce abnormal movement between the vertebrae
Overall, many dogs respond well to surgical treatment. The outcome is, however, dependent on how severe the signs were and how long they have been present before surgery.
CT images of a dog with LS disease – lateral and ventral new bone formation at the lumbosacral junction (yellow arrows); bilateral stenosis of the neuroforamen (blue arrows); irregularities and sclerosis associated with the endplates of both S! and L7 (pink arrows); mild bulging of the L7-S1 intervertebral disc but not causing any compression of the cauda equina (green arrows).
MRI images of a dog with LS disease – the L7-S1 intervertebral disc protrudes into the spinal canal (pink arrow) causing displacement of the caudal equina nerves; the associated spinal nerves are thickened and hyperintense with contrast enhancement, worse on the right side of the images (yellow arrowheads).
MRI images of a dog with LS disease caused by an extradural compression from the L7-S1 intervertebral disc (red arrows) exhibiting marked degenerative changes to the disc in the left image, and milder changes in the right image.
MRI images of a dog with LS disease – extradural lesion in neutral position, causing compression of the cauda equine nerves (red arrows); swollen L7 nerve roots, worst on the left side of the image (yellow arrows).
Post-operative CT images following a dorsal laminectomy, lumbosacral distraction and stabilisation procedure for a dog with dynamic lumbosacral disease.
Next steps
Your regular veterinarian can arrange a consultation with one of our surgeons to assess your dog and discuss what is involved.
Dr Daniel Poletto
BVB DVM
Surgical Resident
If you have concerns for your pet in connection to this condition we recommend discussing it with your primary care vet in the first instance, or get in touch with our team for more information.
If you need urgent medical help, contact our 24 hour Pet Emergency team at Stafford, North Lakes, or Sunshine Coast on 1300 QLD VET (1300 753 838)