Radicular pain is a frequent complaint of patients presenting to outpatient primary care and musculoskeletal clinics. Most cases of radiculopathy are self-limiting, and symptoms resolve over the course of weeks to months. There is spontaneous resolution of disc herniations, and clinical improvement correlates with morphologic resolution. Knowledge of the natural history of radiculopathy is crucial for the health care provider to appropriately counsel and treat patients with this disorder. Although each patient should be managed individually, the favorable prognosis of radiculopathy based on the natural history supports a conservative approach for the initial weeks to months for most patients.
Approximately two-thirds of adults suffer from neck and low back pain. Axial spine pain is often accompanied by radicular pain or radiculopathy, which is defined as spinal nerve root dysfunction causing dermatomal pain and parasthesias, myotomal weakness, and/or impaired deep tendon reflexes. Mixer and Barr first introduced the concept of herniated disc material leading to radiculopathy in 1934. Since that landmark study, extensive research has been conducted on the pathogenesis, clinical presentation, and treatment of radiculopathy. An understanding of the natural history of radiculopathy is crucial because it better enables health care providers to counsel patients, recommend treatments, and assess outcomes of specific interventions. Although it can be challenging to sort through the available information given the vast differences in diagnostic criteria, length of follow-up periods, and exposure of many patients to some type of conservative management, this article aims to combine the findings from several landmark papers to provide a concise summary of the natural evolution of radiculopathy.
Epidemiology
The estimated prevalence of radiculopathy is 9.8 per 1000 and 3.5 cases per 1000 in the lumbosacral and cervical spine, respectively. Patients with lumbosacral radiculopathy tend to present in the late 1920s to 1940s, whereas the peak age of presentation for cervical radiculopathy is in the sixth decade. Various risk factors have been investigated for a causative role in the development of radiculopathy, including gender, prior episodes of neck or back pain, and occupational or recreational factors. Although some studies suggest that radiculopathy occurs more frequently in men, others have shown equal rates between genders. Previous history of axial low back pain is a well-established risk factor for lumbosacral radiculopathy, and a prior history of lumbosacral radiculopathy has been found in patients presenting with cervical radiculopathy. Additionally, prior history of trauma was found in approximately 15% of cases of cervical radiculopathy but this association has not been documented in the lumbar spine. Although there is a correlation between a higher body mass and low back pain, the same relationship does not appear to exist in radiculopathy. Multiple studies have shown a genetic linkage for spinal canal size as well as occurrence of disc herniation and subsequent radiculopathy. In regards to occupational factors, lumbosacral radiculopathy occurs more frequently in patients who have performed jobs requiring manual labor, and who work in positions of sustained lumbar flexion or rotation and who engage in prolonged driving.
Natural history
Lumbosacral Radiculopathy
The first study to follow the clinical course of patients with lumbosacral radiculopathy was written by Hakelius in 1970. Of the 38 patients with a clinical presentation consistent with radiculopathy and a disc herniation demonstrated on myelography, 88% reported that they were symptom-free after 6 months. In 1983, Weber published a paper documenting a prospective study of 126 patients with “sciatica”. These patients were randomized to surgery or conservative management and followed for 10 years. The primary treatment given to the 66 patients in the conservative group was bed rest and paracetamol. Some patients also received physical therapy, but the type and frequency was not documented. Sixty-seven percent of patients in the conservative group reported good to fair outcomes at 1 year, 4 years and 10 years. Saal and Saal conducted another prospective study that was published in 1989. They followed 58 patients with a diagnosis of radiculopathy based on physical examination, imaging, and electrodiagnostic testing. The patients were exposed to minimal treatment, including back school and stabilization exercises. At the conclusion of the 31-week follow-up period, 92% reported a good to excellent outcome and 92% had returned to work. Another paper by Weber and colleagues focused on the short-term evolution of lumbosacral radiculopathy in 208 patients. These patients were placed on bed rest for one week, and then allowed to gradually resume activity. None of the patients underwent physical therapy. After 4 weeks, 70% of patients had marked reduction in pain, which corresponded to functional improvement, and 60% had returned to work. Weber’s studies have also investigated prognostic risk factors of recovery as well as recurrence. The factors that correlated with a poor outcome or prolonged recovery included female gender, psychosocial problems, greater than 3 months sick leave before presentation, and a prior history of radiculopathy. A recurrence of symptoms occurs in approximately 20% of patients.
Cervical Radiculopathy
The course of clinical improvement of cervical radiculopathy is even less well documented than that of lumbosacral radiculopathy. Spurling and Segerberg published one of the first papers that attempted to address this question in 1953. They followed 110 patients with cervical radiculopathy who were primarily treated with 7 to 10 days of bed rest and traction. The average follow-up period was 23 months, and the results showed that 77% of patients had definite improvement. They noted that in the first month, 12% of patients were referred for surgical management, but none of the patients that showed a response to treatment in the first month required surgery. Lees and Turner conducted another early study in 1963. They followed 51 patients with cervical spondylosis and radicular symptoms without myelopathy for 10 to 19 years. Some patients were exposed to conservative treatments, including wearing a cervical collar and manipulation, whereas others did not receive any treatment. At the end of the 10 years, 73% of patients reported having mild or no symptoms. DePlama and Subin found significantly different results in 384 patients with cervical radiculopathy. This study compared surgical to nonsurgical outcomes and found that only 29% of conservatively treated patients attained complete symptom relief. Gore and colleagues followed a group of 205 patients with neck pain, of whom 58% had radicular symptoms. Most of the patients were exposed to one or more treatments, including hospitalization, cervical collar, and oral medications. At the completion of the 10-year follow-up, 43% were pain-free and 79% reported a reduction in symptoms. However, 32% reported persistent moderate to severe pain. Two additional studies from the physiatry literature suggest that 70% to 90% of patients with cervical radiculopathy have a good outcome. However, each of these studies included some type of conservative management, including traction. A more recent study of 563 patients who presented to the Mayo Clinic from 1976 to 1990 also showed that 90% of patients had mild or no symptoms after 4 to 5 years of follow-up. However, one-fifth of patients did not improve and ultimately underwent surgical treatment. Only one study specifically monitored for recurrent symptoms and found that recurrences occurred in 12.5% of patients during a follow-up period of 1 to 2 years.
Evolution of Radiographic Findings
The advent of computed tomography (CT) and magnetic resonance imaging (MRI) has significantly impacted the ability to diagnose and monitor disc herniations in patients with radiculopathy. These imaging studies have also made it possible to follow the natural course of disc herniations and compare the morphologic changes with symptomatic improvement. Key was the first to document the spontaneous regression of a herniated disc in the lumbar spine by myelography in 1945. This phenomenon was confirmed with the use of follow-up CT scans in the lumbar and cervical spine in 1985. Saal and colleagues published a subsequent study in 1990 of 12 patients with documented lumbar herniations on CT. These patients were rescanned at an average of 25 months and the following findings were documented: 46% of subjects had 75% to 100% resorption, 36% had 50% to 75% decrease in herniation size, and 11% had 0% to 50% regression. They found that complete resorption was most frequently seen in the patients who had the largest herniations. However, they did not find a significant correlation between clinical and morphologic improvement. Bozzo and colleagues had similar results regarding morphology of lumbar herniations on MRI: 48% of patients had greater than 70% reduction in size, 15% had a 30% to 50% reduction in size, 29% had no change, and 8% had an increase in size. Overall, 64% of the 69 patients had a reduction in herniation size, and the largest degree of resorption was seen in those with medium and large herniations. Maigne and Deligne established a similar relationship between greater spontaneous resolutions in larger herniations in the cervical spine. Cowan and colleagues performed repeat CT scans on 106 patients one year after being diagnosed with lumbosacral radiculopathy. Disc herniations that decreased or fully resolved were seen in 76% of patients. However, only 26% of disc bulges decreased or resolved. Masui and colleagues found that disc herniation size decreased by 95% in 21 patients who had follow-up MRI imaging 7 to 10 years after being diagnosed with disc herniation and radiculopathy. Cribb and colleagues focused on massive lumbar disc extrusions that obscured greater than 66% of the spinal canal at the time of diagnosis of radiculopathy. They found that after 25 months, 14 out of 15 herniations had completely resolved. Although Komori and colleagues did not find a correlation between clinical symptom and radiological improvement, this finding has been demonstrated in more recent studies. Dellerud and Nakstad followed 92 patients over 14 months with follow-up CT scans and found a strong association between clinical improvement and reduction in the size of the lumbar herniation. They also found that central herniations and disc bulges were less likely to resolve, and the reduction in size of disc bulges was associated with a lesser degree of symptomatic improvement than with disc herniations.
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