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Goichiro Tamura, Nobuhito Morota, and Satoshi Ihara

OBJECTIVE

Sacrococcygeal dimples in neonates and infants are of uncertain pathological import. Previously they were believed to be rarely associated with intraspinal anomalies. Recent studies using MRI, however, revealed that 6%–7% of pediatric cases of sacrococcygeal dimples were associated with anatomical tethered spinal cord (TSC). Because the prevalence of tethered cord syndrome is still unclear, there is no consensus among pediatric neurosurgeons on the management of children with sacrococcygeal dimples. The authors performed an analysis of MRI and urodynamic studies to validate their management strategy for pediatric cases of sacrococcygeal dimples.

METHODS

A total of 103 Japanese children (49 male and 54 female, median age 4 months, range 8 days–83 months) with sacrococcygeal dimples who were referred to the Division of Pediatric Neurosurgery between 2013 and 2015 were included in this study. The lumbosacral region of all the patients was investigated using MRI. Anatomical TSC was defined as a condition in which the caudal end of the conus medullaris is lower than the inferior border of the L2–3 intervertebral disc. Patients with minor spinal anomalies (e.g., anatomical TSC, filum lipoma, thickened filum, or filar cyst) underwent further urodynamic studies to ascertain the presence of neurogenic bladder (NGB). In this study, the presence of NGB without anatomical TSC but with other minor spinal anomalies was defined as “functional TSC.” The prevalence of anatomical and functional TSC was investigated. The association of the following cutaneous findings with spinal anomalies was also assessed: 1) depth of the dimple, 2) deviation of the gluteal fold, and 3) other skin abnormalities (e.g., discoloration, angioma, or abnormal hair).

RESULTS

The children were classified into 4 groups: Group 1, patients with anatomical TSC; Group 2, patients with functional TSC; Group 3, patients without anatomical or functional TSC but with other minor spinal anomalies; and Group 4, patients with no spinal anomaly. There were 6 patients (5.8%) in Group 1, 8 patients (7.8%) in Group 2, 10 patients (9.7%) in Group 3, and 79 patients (76.7%) in Group 4. Twenty-four patients (23.3%; Groups 1, 2, and 3) showed MRI abnormalities, including filum lipoma (14 cases), filar cysts (5 cases), thickened filum (2 cases), and anatomical TSC without other spinal anomalies (3 cases). Untethering of the spinal cord was indicated for 14 patients (13.6%; Groups 1 and 2) with anatomical and functional TSCs. Preoperative NGB was found in 12 patients and improved postoperatively in 7 (58.3%). None of the associated lumbosacral skin findings predicted the presence of underlying spinal anomalies.

CONCLUSIONS

The prevalence of tethered cord syndrome among children with sacrococcygeal dimples was, for the first time, revealed to be higher than previously thought. MRI and supplemental urodynamic studies may be indicated for children with sacrococcygeal dimples to identify patients with symptomatic TSC.

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Nobuhito Morota and Satoshi Ihara

Object

Postnatal improvement in Chiari malformation type II (CM-II) following surgical repair of myelomeningocele was evaluated.

Methods

The authors reviewed data obtained in 20 cases in which patients underwent postnatal myelomeningocele repair within the first 48 hours after birth between October 2002 and September 2006. In 14 patients (Group 1), myelomeningocele was diagnosed in utero and the infants were delivered by cesarean section at 35–39 weeks' gestation (mean 36.4). The 6 infants in Group 2 were born after full-term gestation (39–41 weeks), and their myelomeningoceles were diagnosed postnatally. In all 20 patients, the myelomeningoceles were surgically repaired postnatally. Dynamic change of the herniated cerebellar tonsils in CM-II before and after the myelomeningocele repair, associated hydrocephalus, and symptomatic CM-II were analyzed.

Results

In Group 1, the CM-II was confirmed before myelomeningocele repair in 13 cases (93%). The spinal level of the caudal end of the cerebellar tonsils ranged from C-2 to C-7. Ascent of the cerebellar tonsils was observed in 11 patients (range 1–4 spinal levels, mean 2 levels) and continued even after ventriculoperitoneal (VP) shunt placement in most patients. A VP shunt was required for the treatment of hydrocephalus in 12 patients (86%). Symptomatic CM-II developed in 8 of 13 patients (61%), 3 of whom required surgical decompression.

In Group 2, CM-II was confirmed in 5 infants (83%), with the cerebellar tonsils at a spinal level of C-2 to C-4 or C-5. Ascent of the cerebellar tonsils was observed in 4 patients (range 1–1.5 spinal levels, average 1.1 levels), and no patient had symptomatic CM-II. A VP shunt was placed in 5 patients (83%). No patient was lost to follow-up during the 18-month follow-up period. The only statistically significant difference between the 2 groups was the presence of symptomatic CM-II in Group 2 (p = 0.02).

Conclusions

Patients showed ascent of the cerebellar tonsils after postnatal myelomeningocele repair. Placement of a VP shunt helped promote the ascent. However, postnatal myelomeningocele repair in the patients in Group 1 failed to consistently prevent development of symptomatic CM-II. This limited experience suggests that postnatal repair of myelomeningocele can partially reverse the anatomical CM-II, but symptomatic CM-II cannot be prevented in some patients when the repair is performed after 36 weeks' gestation.

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Nobuhito Morota, Satoshi Ihara, and Hideki Ogiwara

OBJECTIVE

Spinal lipomas are generally thought to occur as a result of failed primary neurulation. However, some clinical features cannot be explained by this theory. The authors propose a novel classification of spinal lipomas based on embryonic changes seen during primary and secondary neurulation.

METHODS

A total of 677 patients with occult spinal dysraphism underwent 699 surgeries between August 2002 and May 2015 at the National Center for Child Health and Development and Tokyo Metropolitan Children's Medical Center. This group of patients had 378 spinal lipomas, including 119 conus spinal lipomas, 27 lipomyelomeningoceles, and 232 filum lipomas, which the authors classified into 4 types based on neural tube formation during embryonic development. Type 1 is defined as pure primary neurulation failure; Type 2 ranges from primary to secondary neurulation failure; Type 3 consists of secondary neurulation failure (early phase); and Type 4 is defined as secondary neurulation failure (late phase). The authors also review embryogenesis in secondary neurulation and analyze the clinical utility of the new classification.

RESULTS

There were 55 Type 1 spinal lipomas, 29 Type 2, 62 Type 3, and 232 Type 4. All filum lipomas fell into the Type 4 spinal lipoma category. Association with anorectal and/or sacral anomalies was seen in none of the Type 1 cases, 15 (52%) of Type 2, 35 (56%) of Type 3, and 31 (13%) of Type 4. Urogenital anomalies were observed in none of the Type 1 or Type 2 cases, 1 (2%) of Type 3, and 28 (12%) of Type 4. Anomaly syndromes were present in none of the Type 1 cases, 6 (21%) of Type 2, 3 (5%) of Type 3, and 16 (7%) of Type 4. Associated anomalies or anomaly syndromes were clearly observed only for Type 2–4 spinal lipomas encompassing failed secondary neurulation. Radical resection was feasible for Type 1 spinal lipomas.

CONCLUSIONS

Secondary neurulation of the spinal cord gives rise to the conus medullaris and filum terminale, which are often involved in spinal lipomas. Formation of spinal lipomas seems to be a continuous process overlapping primary and secondary neurulation in some cases. Association with other anomalies was higher in Type 2–4 spinal lipomas, which included failed secondary neurulation, than in Type 1 lipomas, with failed primary neurulation. On the other hand, radical resection was indicated for Type 1, but not for Type 2, spinal lipomas. The new classification of spinal lipomas based on embryonic stage has the potential for clinical use and agrees well with both clinical and surgical findings. The classification proposed here is still preliminary. Further studies and verification are necessary to establish its clinical utility.

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Nobuhito Morota, Satoshi Ihara, Hideki Ogiwara, and Goichiro Tamura

OBJECTIVE

Chondrodysplasia punctata (CDP), a rare skeletal dysplasia, can lead to cervical spine instability and deformity. However, an optimal neurosurgical intervention has yet to be established. Thus, a retrospective study was conducted to assess the efficacy of various surgical interventions for children with CDP.

METHODS

The authors retrospectively reviewed 9 cases of CDP in which cervical decompression with or without posterior fusion was performed between April 2007 and May 2016. Patient demographics, preoperative clinical conditions, radiographic findings, surgical procedures, and the postoperative course were analyzed in detail.

RESULTS

A total of 12 operations were carried out in 9 patients (8 male, 1 female) during the study period. The patients’ ages at the initial surgery ranged from 2 months to 2 years. Seven of the children had CDPX1, 1 had CDPX2, and 1 had tibia-metacarpal type CDP (CDP-TM). The lesion occurred at the craniovertebral junction (CVJ) in 7 cases and involved a subaxial deformity in 2 cases. The initial surgery was C-1 laminectomy with occipitocervical fusion (OCF) followed by halo external fixation in 5 cases, OCF alone in 1 case, and C-1 laminectomy alone in 3 cases. Three children required additional surgery. In one of these cases, a staged operation was required because the patient’s head was too small to attach a halo ring at the time of the initial procedure (C-1 laminectomy). In another case, OCF was performed 11 months after C-1 laminectomy because of intramedullary signal change on serial MRI, although the child remained asymptomatic. In the third case, additional posterior fusion was performed 17 months after an initial laminectomy and OCF due to newly developed cervical dislocation caudal to the original fusion. This last patient required a third operation 9 months after the second because of deep wound infection. Surgery improved the motor function of all 7 children with CDPX1, but 3 children who had already suffered respiratory failure preoperatively required continued respiratory support. At the time of this report, 7 of the 9 children were alive and in stable condition. One child died due to restrictive respiratory insufficiency, and another died in an accident unrelated to CDP.

CONCLUSIONS

Surgical decompression with or without fusion for CVJ and subaxial cervical lesions in infants and toddlers with CDP generally saves lives and increases the likelihood of motor function recovery. However, in this case series the patients’ preoperative condition had a strong effect on postoperative respiratory function. The surgery was not straightforward, and a second operation was required in some cases. Nevertheless, the findings indicate that early surgical intervention for CDP with cervical involvement is feasible, suggesting that the role of neurosurgery should be reevaluated.

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Yoshiro Ito, Koji Tsuboi, Hiroyoshi Akutsu, Satoshi Ihara, and Akira Matsumura

✓ The authors discuss the results obtained in patients who underwent foramen magnum decompression for longstanding advanced Chiari I malformation in which marked spinal cord atrophy was present. This 50-year-old woman presented with progressive quadriparesis and sensory disorders. Magnetic resonance imaging revealed the descent of cerebellar tonsils and medulla associated with remarkable C1—L2 spinal cord atrophy. After a C-1 laminectomy—based foramen magnum decompression, arachnoid dissection and duraplasty were undertaken. These procedures resulted in remarkable neurological improvement, even after 40 years of clinical progression. Spinal cord atrophy may be caused by chronic pressure of entrapped cerebrospinal fluid in the spinal canal.

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Nobuhito Morota, Satoshi Ihara, Hideki Ogiwara, Kenichi Usami, Ikkei Tamada, and Tsuyoshi Kaneko

OBJECTIVE

The basal encephalocele (BEC) is the rarest form of encephalocele, with an incidence of about 1/35,000 live births. The incidence of its subtype, sphenoidal BEC, is even lower at about 1/700,000 live births. The aim of this study was to propose the optimal surgical approach to repairing BEC, with special attention to the reconstruction of the skull base bone defect.

METHODS

Fourteen consecutive pediatric patients with BEC who underwent surgical repair between March 2004 and March 2020 (10 boys and 4 girls, age 25 days to 7 years, median age 4 months) were enrolled. The follow-up period of the surviving patients ranged from 53 to192 months (mean 119.8 months). The patient demographics, BEC subtypes, preoperative clinical condition, radiographic findings, surgical procedures, and postoperative course were retrospectively analyzed.

RESULTS

There were 4, 8, and 2 cases of sphenoidal BEC, sphenoethmoidal BEC, and ethmoidal BEC, respectively. The size of the bone defect was small in 3 patients, medium in 7, and large in 4 patients. All the patients with sphenoethmoidal and ethmoidal BEC showed associated congenital anomalies other than cleft palate. In total, 25 operations were performed. Two patients underwent multiple operations, whereas the remaining 9 patients received only 1 operation. The transoral transpalatal approach was the initial procedure used in all 14 patients. The transfrontobasal approach was applied as an additional procedure in 2 patients and as part of a 1-stage combined operation in 2 patients. Autograft bone alone was used for skull base reconstruction in 17 early operations. A titanium mesh/plate was used in the remaining 8 operations without any perioperative complications. All BECs were successfully repaired. Three patients died during the clinical course due to causes unrelated to their surgery. All but one of the surviving patients started growth hormone replacement therapy before school age.

CONCLUSIONS

Based on the authors’ limited experience, the key to successful BEC repair involves circumferential dissection of the BEC and a firm reconstruction of the skull base bone defect with a titanium plate/mesh. The transoral transpalatal approach is a promising, reliable procedure that may be used in the initial operation. When a cleft palate is absent, transnasal endoscopic repair is recommended. The transfrontobasal approach should be reserved for cases with a huge BEC and other anomalies. Long-term prognosis is apparently favorable in survivors.