Horse tail syndrome – what it is and how it affects health

n 1595, the French doctor Andre du Laurens described for the first time a structure visibly similar to a bundle of fibers or a rope, located at the lower end of the spinal cord. The bundle of axons (extensions of neurons) was named ” cauda equina “, which in Latin means “horse’s tail”. The cauda equina syndrome is a pathology that describes the damage to the sensory and motor nerves in the cauda equina, which includes nerves in the lumbar, sacral and coccygeal regions. In terms of incidence, approximately 1-3 people out of 100,000 will develop, for relatively different reasons, the cauda equina syndrome.

On the other hand, it has been observed that the most common injuries of the spinal cord that could lead to the cauda equina syndrome are disc herniations at the level of the L5-S1 vertebrae. The horse’s tail includes nerves and nerve roots that originate in the lower end of the spinal cord, that is, at the level of the L1-L5 vertebrae. These nerves provide the motor and sensory innervation of the legs, bladder, anus and perineum. The cauda equina syndrome results from the compression of these nerves, which leads to the interruption of their function. Most frequently, the injuries affect the roots of the L3-L5 nerves. Cauda equina syndrome is, most of the time, a medical emergency.


  1. Horse tail syndrome – causes and risk factors
  2. Horse tail syndrome – symptoms and clinical manifestations
  3. Horse tail syndrome – diagnostic protocol
  4. Horse tail syndrome – treatment options
  5. Horse tail syndrome – complications and associated risks


Horse tail syndrome – causes and risk factors

Cauda equina syndrome is quite rare, but occurs in approximately 3% of all cases of disc herniation. It is most frequently diagnosed among young men, probably as a result of the fact that this population group is much more likely to suffer from thoraco-lumbar compressive trauma. The main cause that can lead to the cauda equina syndrome is lumbar disc herniation. Approximately 45% of diagnosed cases are the result of mechanical compression of the tail of the horse resulting from a lumbar hernia. Other causes that could lead to cauda equina syndrome are the following:

  • epidural abscess;
  • spinal epidural hematoma;
  • discitis (inflammation of the intervertebral disc);
  • the presence of a tumor (either through metastasis or in the form of a cancer of the nervous system);
  • injuries in the lower region of the spinal cord;
  • spinal stenosis;
  • aortic obstruction, thrombosis of the inferior vena cava;
  • wrong chiropractic manipulation;
  • spinal arachnoiditis (inflammation of the arachnoid membrane, which covers the spinal cord);
  • arachnoid cysts;
  • infections ( meningitis);
  • inflammatory conditions, such as ankylosing spondylitis.

In some cases, the cauda equina syndrome can be a secondary complication of an intervention at the level of the spine. However, lumbar disc herniation is the main cause of this condition. Very rarely, chronic constipation can lead, over time, to horsetail syndrome. Other rare causes are gunshot wounds, chemonucleolysis or spinal anesthesia (spinal anesthesia). The main risk factors associated with lumbar herniation are smoking, advanced age, increased body mass index (obesity). Also, axial overload with excessive weights (carrying objects, wrongly performed strength training) and strong blows increase the risk of hernia.

Horse tail syndrome – symptoms and clinical manifestations

The cauda equina syndrome can present itself with various clinical manifestations. Specifically, it presents with acute or progressive bladder dysfunction, with or without chronic back pain and with a frequently present symptom, namely sciatica. Broadly speaking, the cauda equina syndrome is classified into two types, depending on the severity of the injury and the associated symptoms, especially if urinary retention is present or not:

  1. complete:strongly associated with urinary incontinence, loss of perianal sensitivity, along with urinary retention;
  2. incomplete:the need to strain the muscles to eliminate urine, without urinary retention or the sensation of bladder fullness, reduced urinary flow, partial loss of sensitivity around the anus.

Usually, people with cauda equina syndrome may also experience:

  • severe back pain and sciatica (97% of diagnosed people);
  • weakness and paresthesias (tingling, numbness) of the lower limbs;
  • bladder dysfunction (present either in the form of urinary retention or incontinence, up to 92% of people with cauda equina syndrome presenting this symptom);
  • intestinal dysfunction (faecal retention or incontinence, up to 72% of patients having this symptom);
  • numbness, tingling and loss of sensitivity in the buttocks, thighs, hips;
  • erectile dysfunction or impotence (in men);
  • diminished or absent bulbocavernosus reflex.

The loss or diminution of sensitivity in the buttocks, in association with bladder dysfunction, are typical symptoms of the early stages of cauda equina syndrome . Painless urinary retention has the most relevant predictive value in the case of this condition. However, unfortunately, it will often indicate a late stage of the syndrome, often irreversible. In the case of a chronic mechanical compression of the horse’s tail, significant motor deficits may appear, such as the lack of reflexes (at the level of the lower limbs), hypotonia or muscle atrophy. The complete cauda equina syndrome has a less favorable prognosis and surgical outcome than the incomplete one.

Cauda equina syndrome – diagnostic protocol

The gold standard to diagnose cauda equina syndrome is the MRI investigation. If there are contraindications for performing an MRI (for example, in the case of the presence of metal implants), one can opt for CT myelography. Bladder imaging could demonstrate the presence of a postmicturition residual volume, supporting the diagnosis of cauda equina syndrome . As a result of the fact that the cauda equina syndrome is a medical emergency, the MRI investigation and early neurosurgical (or orthopedic) consultation are essential. MRI can also identify possible causes that lead to the cauda equina syndrome, such as lumbar hernia, tumors or stenosis.

Cauda equina syndrome – treatment options

The treatment for the cauda equina syndrome is, in the first instance, surgical. The procedure with the most effective results is the lumbar laminectomy, which removes the structure that puts mechanical compression on the nerves at this level. It should be mentioned that the success of this intervention is closely dependent on the time and place. Studies claim that if the intervention takes place within 24-48 hours of the appearance of associated symptoms, there is a much better rate of resolution and recovery is much easier. Early surgical intervention prevents permanent damage to the nerves, improving the subsequent recovery of functions.

Horse tail syndrome – complications and associated risks

Several studies have analyzed the prognosis or outcomes associated with cauda equina syndrome, depending on when the surgical decompression of the affected nerves took place. It is known that early intervention, within no more than 48 hours from the onset of the signs associated with cauda equina syndrome, has the best prognosis. The longer the compression persists, the more severe the structural and functional damage to the nerves, so we are talking about a much more reserved prognosis. The presence of bladder dysfunction in people who were later diagnosed with cauda equina syndrome was associated with poor therapeutic results.

Complications associated with cauda equina syndrome occur in most people who suffer from this condition. Epidemiological data suggest that a large percentage of people with this syndrome end up having residual symptoms, regardless of the time of surgical decompression. Bladder retention and urinary incontinence are complications present in approximately 48% of diagnosed people. Even if intestinal dysfunction is reduced after the operation, it has been observed that up to 42% of patients may present intestinal dysfunction even after 60 days. Sexual dysfunction, sciatica and loss of perianal sensitivity can sometimes persist.


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