Cauda Equina Syndrome
(The "Horse's Tail" Fights Back)
The cauda equina is an anatomical term given to all of the nerves that dangle off the end of the spinal cord. In fact, in Latin, the term cauda equina means "horse's tail". The dangling nerves are housed in the thecal sac, and are normally bathed in a sea of cerebral spinal fluid. Each of the nerves in the cauda equina eventually branches from the thecal sac. From there they exit the spinal column and travel to their respective target organs and/or muscles.
Cauda equina syndrome occurs when the nerves in the "horse's tail" get squished by some pathologic process. The most common pathology is a large herniated intervertebral disc that pushes back on the thecal sac. Other causes include tumors, blood clots (ie: hematomas), traumatic injuries such as burst fractures or fracture dislocations, severe lumbar stenosis, as well as abscesses.
Regardless of the cause, when the nerves get impinged they are unable to perform their functions. This leads to the classic signs and symptoms of cauda equina discussed below.
The classic teaching is that cauda equina syndrome presents with the acute onset of lower extremity weakness, poop incontinence (ie: fecal incontinence if you want to be "scientific" about it), urinary retention (ie: patient cannot pee), loss of leg reflexes, low back pain, sexual dysfunction, and loss of sensation, especially in the "saddle" and peri-anal region.
It is important to note that patients with cauda equina syndrome rarely present with all these symptoms. The most worrisome symptoms are sudden weakness and bowel or bladder issues.
Additionally, radicular type symptoms such as numbness and tingling or sharp pains down the legs can also be present.
Overall, there is no one definition of cauda equina syndrome. Unfortunately, there are numerous definitions in the scientific literature based on different permutations of the above signs and symptoms.
It is also important to distinguish between acute and chronic forms of the syndrome. Acute symptoms occur with rapid onset and require emergent evaluation. However, many patients have evidence of chronic dysfunction of the nerves that compose the cauda equina; their symptoms have been slowly evolving over months or years (ie: think older people with lumbar stenosis). The rapidity of evaluation is less important in these cases, but should still be undertaken.
The time frame in which cauda equina symptoms develop is important for determining optimal treatment, and providing patients with a realistic prognosis for recovery.
Diagnosis is based on the combination of appropriate symptoms in conjunction with MRI or CT myelogram images that show significant compression of the cauda equina.
In addition to a thorough neurological examination, patients with suspected cauda equina syndrome should also have a post void residual (PVR) measurement taken. PVRs help diagnose urinary retention, which is a classic and worrisome symptom.
"True" acute cauda equina syndrome caused by a large mass pushing on the nerve roots is managed with emergent surgical decompression. Typically, a laminectomy (ie: a procedure in which part of the bone in the back of the spinal column is removed) is performed to relieve pressure on the thecal sac.
Other therapies including antibiotics for abscesses/infections, chemotherapy for tumors, and steroids for inflammatory causes.
Cauda equina syndrome is caused by compression of the nerves in the thecal sac. Classic symptoms include weakness, saddle anesthesia, fecal incontinence, and urinary retention although no exact definition in the scientific literature exists. Furthermore, both acute and chronic forms of cauda equina syndrome exist based on the rapidity of symptom onset. Diagnosis is based on clinical signs and symptoms in conjunction with MRI or CT myelogram imaging that reveals compression of the nerves.Atlanto-occipital dislocation
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