Chinese Abstract OBJECTIVE: To analyze the factors affecting the development and prognosis of common embryogenic tumors of cone cauda equina and to find ways to improve the efficacy. METHODS: A retrospective study of 23 cases admitted to our hospital in recent years. The correlation of each clinical factor with preoperative neurological functional status and prognosis was analyzed. RESULTS: There were 11 cases of epidermoid cysts, 9 cases of teratoma, and 3 cases of dermatomal cysts. Preoperative sensorimotor function correlated with time of onset, and preoperative urinary and fecal function correlated with longitudinal diameter of the tumor. All cases were treated by microsurgery and followed up for 3 months after surgery. The postoperative recovery of sensorimotor function was good and correlated with the preoperative functional status and time of onset. The recovery of urinary and fecal function was poor and correlated with the preoperative functional status of urinary and fecal function. Both preoperative neurological function and postoperative recovery were independent of the type of pathology. Conclusion: The main factor affecting the prognosis is the preoperative neurological functional status, and early diagnosis and early surgery can significantly improve the prognosis of patients. Keywords: cone, cauda equina, dermatomal cyst, epidermoid cyst, teratoma, cone, cauda equina, embryogenic tumors are rare, mostly dermatomal cysts, epidermoid cysts and teratomas with similar clinical features. teratomas were first reported by Gowers in 1876 [1], these tumors are prone to urinary and fecal dysfunction and the outcome has been poor. In this study, we retrospectively analyzed 23 cases of this type of tumor admitted to our hospital in recent years (1997, 1-2007, 3) to study the factors affecting patients’ preoperative neurological function and prognosis, and reviewed the literature to explore ways to improve the outcome. Materials and methods 1. Inclusion criteria: Invasion of the conus and/or cauda equina, pathologically confirmed and with corresponding symptoms. Exclusion criteria: those with lesions involving the spinal cord above the conus or those who were not operated. 2. General data: There were 23 cases, 16 males and 7 females. The average age of onset was 23,7±10,9 years, with the youngest being 2 years old and the oldest 49 years old. From the onset to surgical treatment, the shortest was more than 20 days, the longest was more than 10 years, and the average was about 3,12 years. 3. Clinical manifestations: all had sensory-motor dysfunction before surgery, including low back pain (14, 60, 9%), lower extremity pain (19, 82, 6%), abnormal sensation in the saddle area (9, 39, 1%), abnormal sensation in the lower extremity (12, 52, 2%) and lower extremity motor impairment (12, 52, 2%). According to McCormick’s classification, preoperative grade I was common (11,47,8%), grade III was not uncommon (8,34%), and grade II was found in 4 cases (17,4%). Preoperatively, most of the patients had urinary and fecal dysfunction (12, 52, 2%), including urinary dysfunction (11, 47, 8%) and fecal dysfunction (10, 43, 5%). The most common first symptom was pain (18,78,3%), while urinary and fecal dysfunction (3,13%) and lower limb motility disorders (2,8,7%) were rare. In addition, the key reflexes of the lower limbs were weakened or disappeared in 15 cases, muscle atrophy of the lower limbs was present in 7 cases, and the testicular reflexes were weakened or disappeared in 5 cases and anal flaccidity in 2 cases in male patients. 4. Imaging examination: MRI was performed in all cases, characterized by mixed signal, no enhancement in the center of the tumor, and some tumor edge enhancement. The maximum transverse diameter was 2.5cm, the minimum was 0.74cm; the maximum longitudinal diameter was 8.6cm, the minimum was 2cm. 9 cases were combined with malformation. 5. Surgical methods: All of them were treated by microsurgery, and all of them invaded the cauda equina nerve and 17 cases invaded the conus at the same time. The dural tension was high, and there were often extensive adhesions around the tumor, which were cord-like and sometimes difficult to distinguish with the naked eye. In all cases, the tumor was excised first, and bean-like material, hair, fat and bony material were seen. For the conical part of the tumor, an incision is made from the most bulging part of the tumor. The tumor wall should be excised as much as possible, and the tumor wall closely related to the nerve should not be separated forcibly. If there is residual fatty tissue closely related to the spinal cord and nerves, total excision is not forced. The operation is strictly intracapsular, with hydrocortisone saline flushing in the field and low-power electrocautery treatment of the residual capsule wall. For some deformities such as dermatomal sinus, the spinal cord traction was removed at the same time, and the spinal cord traction was released by cutting the end filaments and loosening the adhesions. Results 1. Surgical effect: All tumor contents were excised, 7 cases of total excision of tumor wall and 16 cases of sub-total excision. The cones were cut in 7 cases, but the nerve roots were not cut. 2. Postoperative pathology: 11 cases of epidermoid cyst, 9 cases of teratoma, and 3 cases of dermatomycosis were found in the postoperative pathology. 3. Follow-up: At 3-month follow-up, 20 cases (87%) showed improvement in sensorimotor function, among which those with preoperative McCormick grade I (11 cases) and grade II (4 cases) showed improvement, and 5 cases with grade III (8 cases) showed improvement. Among the Grade III cases, 2 cases showed no change and 1 case worsened (4%). 5 of the 12 cases with urinary and fecal dysfunction improved after surgery (41,7%), while 5 cases worsened (41,7%) and 2 cases showed no significant change (16,7%). There was also one case of newly developed postoperative dysfunction. 4. Statistical results: The patients’ age, time of onset, cone involvement, pathological type, transverse and longitudinal tumor diameter and preoperative neurological function status (McCormick’s classification and presence of urinary and fecal dysfunction), as well as preoperative neurological function status, time of onset, cone involvement, pathological type, extent of resection, transverse and longitudinal tumor diameter and postoperative neurological function changes (improvement was judged as good, no The χ2 test (counting data) or t-test (measurement data) was performed.) The data were analyzed using SPSS 13, 0 software. In addition, preoperative McCormick classification was significantly associated with the prognosis of sensorimotor function (χ2=6, 469, P=0, 039). Preoperative urinary and fecal functional status was significantly correlated with the prognosis of postoperative urinary and fecal function (χ2=6, 135, P=0, 013). Discussion Early diagnosis and microsurgical treatment are the most important factors to improve the prognosis of patients [2]. The better recovery in our group of cases with early surgery for sensory-motor disorders correlated with the time of onset, indicating the importance of early diagnosis and early surgery. The recovery of both sensorimotor and continence functions correlated with preoperative function [3]. The preoperative sensorimotor function correlated with the time of onset, and the preoperative bowel and urinary function correlated with the longitudinal diameter of the tumor, which also indicates that the surgery can achieve better results when the tumor is small, the adhesions are mild, and the neurological function, especially the bowel and urinary function, is not significantly impaired. The advancement of microsurgery technology can improve the resection rate of tumor and reduce the damage to nerve tissue, which is beneficial to improve the prognosis. However, early symptoms are not characteristic and easy to be misdiagnosed or missed, and MRI helps to improve the early diagnosis rate [4-6]. Tumors in this area tend to cause urinary and fecal dysfunction, and once they appear, the prognosis is poor and affects the quality of life of patients [7-9]. The present study showed that the recovery of postoperative continence function correlated with preoperative continence function, indicating that once continence dysfunction appeared, recovery was mostly poor even with active treatment. The present study also found that preoperative continence function was correlated with the longitudinal diameter of the tumor, independent of whether the cone was involved, revealing that the patient’s dysfunction may be mainly related to the extensive involvement of nerve roots due to the longitudinal growth of the tumor along the spinal canal. In contrast, whether the cone is damaged or not has no significant effect on the prognosis, which we believe is related to the fact that the tumor is mostly cystic and soft in texture, so the compression or destruction of the cone may be a relatively minor factor. This shows that urinary and fecal dysfunction is common and poorly recovered, and it is very important to operate before severe urinary and fecal dysfunction occurs. In this group of cases, the type of pathology had no significant effect on prognosis, suggesting that in this type of tumor, a small amount of residual tumor wall or fat has no effect on the near-term recovery as long as there is no malignancy. There is no obvious boundary between some tumors and normal nerve tissues, which is difficult to distinguish even with the help of microscope. If the tumor wall with tight adhesions is barely separated, it may easily cause damage to nerve tissues. There is no significant correlation between the degree of cyst wall resection and prognosis in this group of patients, and even the proportion of improved sensorimotor function is lower in those with total resection than in those with subtotal resection, which also indicates that tightly adherent tumors should not be forcibly separated [5, 10, 11]. However, the tumor contents should not remain, and the protection of the operative field should be enhanced with repeated flushing with dexamethasone saline [12]. Moreover, tumor growth is slow, and sub-total resection can achieve symptomatic improvement for a long time [1], and even if recurrence occurs, reoperation can also relieve symptoms [13] (but recurrence is more likely in malignant change [14]), so cyst excision should be performed to ensure neurological function, strictly confined to the capsule, without reluctantly separating the tumor, or even just for cyst contents removal and cyst wall exenteration suture can be performed [5]. Therefore, with the use of microsurgical techniques, adequate removal of tumor contents, removal of the tumor wall as much as possible, and reduction of nerve tissue damage, surgery can mostly achieve good results [1, 3, 15]. As for the long-term outcome, further observation is needed. Severe spinal deformities can lead to compromised neurological function and prognosis. However, the combined deformities in our group had no significant effect on preoperative function and postoperative recovery. We believe that mild deformity is not the main factor affecting preoperative neurological function, and with reasonable treatment, better treatment results can be obtained. The recurrence of tumor is mainly related to tumor remnants [5, 14, 16], so the remaining cyst wall should be treated appropriately. In our group of cases, low-power electrocautery was used with good results as an effective way to deal with the cyst wall [14]. Chemical treatment such as iodine cautery has also been used [17]. In cases where the cyst wall is not completely excised, the patient’s AFP level should be monitored postoperatively [14] and MRI should be reviewed if necessary.