Learning Objectives Key Points
- Cauda equina syndrome has symptoms similar to those of peripheral nerve dysfunction
- Treatment of cauda equine syndrome has a variable outcome
- A similar condition, conus medullaris syndrome, is often confused with cauda equina syndrome
History
A 66 year old man is sent to the office urgently because he has developed trouble walking. He has a significant medical history of lymphoma. He explains that the symptom began gradually, starting with numbness affecting his thighs, then weakness of his legs, accompanied by sharp pains in the areas of the thighs. It has bothered him for about three weeks and it has become gradually worse. He started walking with a cane, now he is using a walker. Physical therapy was not helpful for treating the symptoms. He has had trouble controlling his bowels and his bladder, and he feels reduced sensation in the perineal region. He denies constipation or urinary retention. He has not had significant back pain or an injury.
He has a past medical history of non-Hodgkin lymphoma, treated by cyclophosphamide, vincristine, prednisone, and rituximab. He completed his last treatment about one year ago.
At this time, he takes no medications, and he has no allergies to medications.
He is a previous smoker, stopping 18 months ago. Prior to that, he smoked one pack of cigarettes per day for 45 years. He does not drink alcohol. He is a retired grocery clerk.
There is a family history of diabetes mellitus and hypertension.
Review of systems is negative for weight loss, fever, rash, dyspnea, chest pain, bruising, bleeding, joint pain or swelling. Bowel and bladder function are abnormal as above. He has not had headaches, tremor or visual symptoms.
Examination
Vital signs show a temperature of 97.5 F, pulse 82, blood pressure 141/83. He is a mildly overweight man who walked slowly into the office with a walker. He appears alert and attentive. His cardiovascular exam is normal. Pupillary and funduscopic exams are normal. He has normal orientation to the place, date, day, year, and current events. He has normal three word recall and attention. He has normal comprehension and naming abilities. He seems fluent. His eye movements are normal in horizontal and vertical directions. There is no nystagmus, and visual fields are full. Facial movement is normal on both sides. Hearing is normal to finger rub. There is normal facial sensation to pin prick. The tongue excursion is normal. Palatal movement is symmetric. Gag reflex is intact on both sides. Shoulder shrug and head thrust are normal. The strength is 5/5 in the deltoid, biceps, triceps, EDC and intrinsic hand muscles on both sides. Strength in the legs is abnormal. Hip flexion is 4/4 (right/left). Hip extension is 5/5. Knee extension is 4/4. Knee flexion is 4/4. Ankle dorsiflexion is 3/3. Plantar flexion is 3 / 4. Movement of the toes appears weak. Deep tendon reflexes in the biceps and triceps are 2/2. They are absent in the quadriceps and gastrocs on both sides. The toes go down to plantar stimulation. Pin sensation is normal in the arms and the trunk. It is impaired in the inner thigh, the perianal area, and the perineum. It is normal in the in the lower legs. He was unable to perform heel knee shin maneuvers. He has normal finger nose finger maneuvers. He could stand, but he moved very slowly, with bent knees, and support his weight with his arms to prevent falling.
Localization and Neuroanatomy
The clinical observation of hyporreflexia, weakness, and saddle distribution anesthesia is key to the diagnosis of cauda equina syndrome. These symptoms are typical of peripheral nerve pathology, and they suggest lower motor neuron findings. Yet the area affected is not really typical of a peripheral nerve process, considering it is bilateral, affects only short nerves, and involves a very specific area. The saddle region of the human body is supplied by sacral nerve roots, which normally course together in the cauda equina. This is the only localization that could cause these symptoms.
Often cauda equina syndrome is confused with an illness that affects a nearby structure- the conus medullaris. There are significant differences between these conditions. Conus syndrome results in hyperreflexia, urinary retention and constipation, cauda syndrome results in hyporeflexia, urinary and bowel incontinence. Both of these can cause numbness, and both of these may cause weakness.
Causes of cauda equina syndrome include spinal stenosis, infiltrative malignancy, infection (epidural abscess), hematoma, trauma and certain inflammatory conditions. Unless trauma is suspected, malignancy is a likely cause, and should be assessed by MRI of the lumbar spine. If this evaluation is normal, then testing with CSF analysis and sometimes EMG is needed to sort out other causes.
Some of the causes of conus medullaris syndrome are different than those of cauda syndrome. A stroke of the spinal cord may cause conus syndrome. Primary CNS tumors, such as glioblastoma, may also affect the conus. Neither of these causes tends to cause cauda syndrome.
Treatment
When cauda equina syndrome is caused by malignancy, there may be a poor clinical outcome. Metastatic malignancy rather than primary neoplasm is common. Forms of cancer that affect this part of the nervous system tend to have a reduced response to aggressive therapy. Chemotherapy, radiation and sometimes surgery are indicated in these cases, depending on the type of malignancy. Radiation oncology and neurosurgery consultations are important to the care of a patient with this condition.
When cauda equina syndrome is caused by spinal stenosis, surgery is often helpful. It depends on the extent of weakness and nerve damage. Recovery is related to duration and clinical severity. Severe, long-lasting cases have a limited recovery.
Review Questions
- Cauda equina syndrome would be most suspicious if
a. a patient experienced numbness in the lower legs and feet, and had diminished ankle and knee reflexes
b. a patient experienced leg numbness and bladder incontinence
c. a patient experienced saddle numbness and diminished ankle and knee reflexes
d. a patient had difficulty walking and leg numbness
e. All of the above - Cauda equina syndrome is difficult to treat. The reason for this is
a. the cause of cauda equina syndrome is seldom found
b. the conditions that lead to cauda equina syndrome resist treatment
c. cauda equina syndrome is often misdiagnosed
d. the treatment for cauda equine syndrome is not known
e. surgical treatments for cauda equina syndrome are not yet optimized - Significant differences between the clinical presentations of cauda equina syndrome and conus medullaris syndrome include
a. numbness affecting the legs
b. weakness affecting the legs
c. diminished reflexes vs. increased reflexes
d. loss of bladder or bowel sensation
e. bladder or bowel leakage vs. retention
f. both C and E