Spine Diseases (Spinal Canal Stenosis)

Spinal stenosis (narrowing) is the narrowing of the sagittal diameter of the spinal canal, the lateral recesses and the foramina (nerve root canals) to a certain degree, either along the entire spinal canal or at one or two vertebrae. It may be congenital, but it can also develop later in life.

The normal sagittal diameter of the lumbar spinal canal is 15-25 mm. The fundamental problem in spinal stenosis is an inadequate canal diameter. If the sagittal diameter is less than 10 mm, it is termed absolute stenosis; if it is between 10-13 mm, relative stenosis is referred to. A specific area called the lateral recess is bounded anteriorly by the posterior surface of the vertebral body, laterally by the pedicle, and posteriorly by the superior articular facet, and it opens medially into the spinal canal. In the lower lumbar region, the distance from the posterior surface of the vertebral body to the most ventral part of the superior articular facet should be no less than 3-4 mm. A lateral recess height of less than 3 mm suggests lateral recess stenosis, while a height of less than 2 mm is diagnostic. Structural changes such as age-related changes, trauma, thickening of the ligaments, joint changes and the development of spondylotic bars may compress neural elements; stenosis may remain asymptomatic unless it falls below a critical level. Stenosis may affect both the cervical and lumbar regions at the same time, but symptomatic stenosis in both regions simultaneously is not common. Symptoms appearing in older individuals are related to myelopathy.

Spinal stenosis can generally occur at any age, but it often begins to produce symptoms after the age of 50. It is more common in men. The L3, L4 and L5 levels are more frequently affected. Patients often complain of insidious back, hip, leg and calf pain. The spread of pain to the legs and arms varies depending on the level of narrowing; the spread is usually bilateral. Walking and standing for long periods trigger the pain. Patients tend to walk in a stooped, forward-bent posture. They find relief from the pain by sitting. This picture is a distinctive condition and is called neurogenic claudication. This pattern distinguishes neurogenic claudication from disc pain, which does not resolve with sitting. As the condition progresses, sitting and lying down also fail to relieve the pain. In advanced cases, persistent pain and urinary problems may develop. Therefore, in cases where spinal narrowing is suspected, urinary urgency and frequent urination are considered important signs for surgery, and patients in this situation are recommended urgent surgery. Patients with spinal stenosis have a very long history of pain and may manage for a while with drug treatment. As stenosis increases, the patient's pain no longer responds to virtually any treatment. Surgery is recommended for these patients.

On physical examination of patients, flattening of the lumbar curve and restriction of range of motion, particularly in backward bending, are found. Bending forward reduces the pain. Specific nerve root compression findings are generally rare. The passive straight leg raise test is negative. Provocative tests such as strenuous physical activity may reveal small strength losses in the lower extremities. Sensory changes may be found particularly in the L4 and L5 distributions. Age, insidious onset, long-standing history and bilateral involvement generally differentiate spinal stenosis from other spinal pathologies. Disc herniations (lumbar hernias) are generally seen in younger people. The pain distribution is usually unilateral and neurological findings are more prominent. Central disc herniations may mimic stenosis with bilateral pain distributions, but the onset of pain is sudden. Pain increases with sitting, and the straight leg raise test is positive.
In vascular claudication, seen in people with vascular insufficiency, pain increases with walking and decreases with rest and short walks. Nevertheless, examination of peripheral pulses is a routine part of the examination of all patients suspected of having spinal stenosis. The best provocative test for differentiating neurogenic and vascular claudication is the bicycle test. During this test, pain occurs in both types, but because the lumbar region is in flexion in stenosis, pain aggravation is less than in the vascular type. Patients with peripheral neuropathy also show pain and sensory deficits that may be confused with stenosis. EMG is useful in the differential diagnosis of these patients. In diagnosing spinal stenosis, four-view lumbosacral radiography, computed tomography (CT) and MRI are used. 80% of patients with stenosis show electrophysiological changes. This test can also more accurately show the areas planned for decompression. Drug therapy is the most frequently used non-surgical treatment in stenosis cases. Nonsteroidal anti-inflammatory medication has been shown to markedly reduce back and leg pain. In situations where the patient is not a suitable surgical candidate or where surgery must be postponed, epidural steroid injection may be tried. Corsets or other belt-type devices have no place in the treatment of spinal stenosis.

Patients who have received an adequate duration and dose of drug therapy without benefit are candidates for surgery. In patients with severe spinal stenosis, physical therapy is unnecessary and may even be harmful at times. If standing weakness and problems with urination and bowel movements have developed, urgent surgery should be planned for the patient. If such symptoms developed before surgery, there is a risk that they will not improve after surgery. The fundamental surgical principle in spinal stenosis is spinal decompression, which prevents compression of the bone and soft tissue elements on the dural sac and spinal nerve roots. There are no clearly defined limits for decompression. This surgical limit depends on each individual's specific anatomy. Central canal stenosis decompression is the easiest stenotic syndrome to treat. The basic procedure is to expose the spinous processes through a midline approach. Then the spinous processes and laminae are excised without touching the facet capsules. Decompression should begin away from the area of maximal stenosis. In medial facetectomy, if the dura is still compressed despite removal of the spinous process and lamina, and dural pulsation is considered insufficient, the superior articular facet may be partially resected. Significant instability does not develop when resection of up to 50% of the facet joint is performed. In lateral recess stenosis decompression, if the patient's stenotic condition is consistent with lateral recess involvement, entry is made through a midline approach, but the lateral recess is enlarged by exposing only the lamina and spinous process on the affected side.

Instability after decompression is not a rare complication. If microsurgical techniques are not used and the facet joints are removed excessively, the risk of instability increases. In these patients, placing screws in every patient to guard against instability is not an appropriate approach. Other complications that may occur during surgery include dural tear, injury or avulsion of nerve roots, dural adhesions and meningitis. Dural tear occurs especially in about 5% of patients with very severe spinal stenosis and must be repaired immediately. Otherwise, cerebrospinal fluid leaks from the back after surgery and significantly increases the risk of meningitis. For the patient to get the maximum benefit from surgery, it is essential that the patient return to their ideal weight after the operation. Hospital stay after surgery is between 1 and 3 days. It is recommended that the patient rest at home for the first week. It is recommended that the patient take short walks outside between 1 week and 20 days, and resume normal daily life after 20 days.