Study Design:The natural process of clinical manifestation, imaging features and laboratory outcomes in 39 patients with cauda equina syndrome were followed up and studied.Objectives:To study the natural characteristics of clinical cauda equina syndrome and to put forward to its clinical classification according to the clinical symptoms, imagings and prognosis.Summary of Background Data:Clinical findings often confused among the patients with cauda equina syndrome.The curative effect and prognosis of different cases were also changeable and uncertain.Little has been reported on the reasonable treatment and mechanism of clinical cauda equine syndrome formation.Methods:39 patients with cauda equina syndrome resulted from different etiologies had been selected and classified according to the slight and severe degree of clinical features.All cases had been treated with surgery decompression operation and followed up after treatment in order to assess its function recovery condition after operation.Clinical features, imaging findings, etiology, sexual, stool and urine functions as well as Electrophysiological (BCR, ICR) in each patients were studied and compared before and after operation.Results:The main clinical manifestations of canda equina syndrome included saddle sensory disturbance bilaterally, and fecal, urinary and sexual dysfunctions.8 of 39 cases appeared abnormal BCR and ICR only and mined normal after decompression surgery in lmbar spine;9 of 39 patients occurred saddle sensory disturbance along with electrophysiological abnormal, and the sensory disturbance disappeared after treatment.9 of 39 cases with severe sensory disturbance ,bowel or bladder dysfunction and sex functional decreased.13 of 39 cases with saddle sensory disappeared, bowels relieved irretened and sexually ability disappeared ,These patients had poor function recovery after operation.The clinical symptoms of patients with multiple segmental canal stenosis on the images had more severe than that of patients with single segmental stenosis(P<0.05).Conclusion:The mechanism of CES is the problem occurred in the reflex arch of which consists of the anus, vesical sphincter, cavernous body, efferent and afferent nerves, and conus medullaris.Bilateral radiculopathy or sciatica are early and critical form of CES and indicates a high risk for the development of clinical feature on the late stage of CES.CES can be classified as 4 stages in clinical practice : preclinical, early, middle and late stages.Electrophysiological abnormal and saddle sensory function decreased are indices for early diagnosis.Patients in preclinieal and clinical early had good function recovery than that of patients in other stages after surgical decompression.