Type 1.5 split cord malformation

Type 1.5 split cord malformation

A subtype of split cord malformation with combined characteristics of types I and II.

A 11-year-old male child, presented with low backache after trivial trauma. He was neurologically intact. Imaging revealed low lying tethered cord and a midline ventral bony spur (D12, L1) with a single dural sac encasing both the hemi cords. Surgical exploration revealed a ventral bony spur with two hemicords, enclosed in a single dural tube. Excision of the bony spur and detethering of the filum terminal was done. Post-operative course was uneventful and the patient was discharged satisfactorily.

SCMs possibly represent, a continuum of changes beginning at the gestational age of day 20-30. Terminologies like mixed or intermediate type, are used to denote SCMs that showed features of both type 1 and type II.

Meena et al. prefered using type “1.5 SCMs” for all such cases, thereby avoiding confusion and maintaining uniformity in nomenclature. However, further experimental studies are required to substantiate our understanding of these complex embryological anomalies on the basis of currently available hypotheses.

This case doesn’t fit into this classification scheme and try to elucidate its embryological basis, with review of relevant literature. They also attempt to include this variety into the existing classification system of SCMs. 1).

A 52-year-old woman had hemicords within a single dural sac with a dorsal bony septum at the L5 level. A 9-year-old boy had hemicords within a single dural sac with a ventral bony septum and fibrous extension at the L3 level. Both patients underwent microsurgical treatments for removing the bony septum, detethering the spinal cord, and sectioning the filum terminale. The surgical procedure revealed an extradural partial bony septum and hemicords within an intact single dural sac in each patient. Both patients were discharged from the hospital without de novo nerve dysfunction. Published cases have validated that types I and II SCM can overlap.

Sun et al. recommend recent type 1.5 SCM as a normative terminology for this overlapping SCM and report two rare cases of this SCM.

They proposed an associated pathogenesis consisting of uneven distribution and regression to explain type 1.5 SCM. Furthermore, they postulate that the amount of condensing meninx primitiva might determine whether the left bony septum has fibrous extensions to the opposite dura in type 1.5 SCM 2).


Meena RK, Doddamani RS, Gurjar HK, Jagdevan A, Chandra SP. “Type 1.5 split cord malformations: an uncommon entity”. World Neurosurg. 2019 Sep 23. pii: S1878-8750(19)32506-9. doi: 10.1016/j.wneu.2019.09.076. [Epub ahead of print] PubMed PMID: 31557552.

Sun M, Tao B, Luo T, Gao G, Shang A. Type 1.5 Split Cord Malformation : A New Theory of Pathogenesis. J Korean Neurosurg Soc. 2021 Nov 22. doi: 10.3340/jkns.2020.0360. Epub ahead of print. PMID: 34802216.

Gamma Knife radiosurgery for cavernous malformation

Gamma Knife radiosurgery for cavernous malformation

Stereotactic radiosurgery (SRS) is a therapeutic option for repeatedly hemorrhagic cavernous malformations (CMs) located in areas deemed to be high risk for resection. During the latency period of 2 or more years after SRS, recurrent hemorrhage remains a persistent risk until the obliterative process has finished. The pathological response to SRS has been studied in relatively few patients.

Gamma Knife radiosurgery (GKRS) has been used to treat cavernous malformations (CMs) located in basal ganglia and thalamus. However, previous reports are limited by small patient population.

Hu et al. retrospectively reviewed the clinical and radiological data of 53 patients with CMs of basal ganglia and thalamus who underwent GKRS at West China Medical Center between May 2009 and July 2018. All patients suffered at least once bleeding before GKRS. The mean volume of these lesions was 1.77 cm3, and the mean marginal dose was 13.2 Gy. After treatment, patients were followed to determine the change in symptom and hemorrhage event.

The mean follow-up period was 52.1 months (6.2-104.3 months). The calculated annual hemorrhage rate (AHR) was 48.5% prior to GKRS and 3.0% after treatment (p < 0.001). The Kaplan-Meier analysis revealed that 2-, 3-, and 5-year hemorrhage-free survival were 88, 80.9, and 80.9%, respectively. Preexisting symptoms were resolved in 11 patients, improved in 14, and stable in 5. Only 2 patients (3.8%) developed new neurological deficit.

This study suggests that AHR after GKRS was comparable to the recorded AHR of natural history (3.1-4.1%) in previous studies. GKRS is a safe and effective treatment modality for CMs of basal ganglia and thalamus. Considering the relative insufficient understanding of natural history of CMs, future study warrants longer follow-up 1)

Wen et al., from the West China Hospital performed a meta-analysis is to evaluate the clinical efficacy of gamma knife radiosurgery for treating cavernous malformation.

PUBMEDOVID EMBASE, and OVID MEDLINE electronic databases are searched. The primary outcome is hemorrhage rate and this meta-analysis is performed with REVMAN 5.3.

9 studies are included in this meta-analysis. The overall RR of hemorrhage rate of pre-GKRS and post-GKRS is 6.08(95% CI: 5.04-7.35). The overall RR is 3.03(95% CI: 2.65-4.11) between the hemorrhage rate of pre-GKRS and the first 2 years of post-radiosurgery, and the overall RR is 12.13 (95% CI: 1.73-85.07) comparing pre-GKRS with 2 years after GKRS. There is no significant difference of the hemorrhage rate between the first 2 years of post-radiosurgery and 2 years after GKRS (RR =2.81, 95% CI: 0.20-13.42). The neurological deficiency is the commonest radiosurgery related complications.

Patients with cerebral CMs, especially who were deep seated and surgically inaccessible, seems to benefit from GKRS due to a reduction of annual hemorrhage rate in the first 2 years, and after that time, despite of a number of cases that suffer from negative side effects of radiation 2).

Between 1993 and 2018, 261 patients with 331 symptomatic CCMs were treated by GKS. The median age was 39.9 years and females were predominant (54%). The median volume of CCMs was 3.1 mL. The median margin dose was 11.9 Gy treat to a median isodose level of 59%. Median clinical and imaging follow-up times were 69 and 61 months, respectively. After the initial hemorrhage that led to CCM diagnosis, 136 hemorrhages occurred in the period prior to GKS (annual incidence = 23.6%). After GKS, 15 symptomatic hemorrhages occurred within the first 2 years of follow-up (annual incidence = 3.22%), and 37 symptomatic hemorrhages occurred after the first 2 years of follow-up (annual incidence = 3.16%). Symptomatic radiation-induced complication was encountered in 8 patients (3.1%). Mortality related to GKS occurred in 1 patient (0.4%). In conclusion, GKS decreased the risk of hemorrhage in CCM patients presenting with symptomatic hemorrhage. GKS is a viable alternative treatment option for patients with surgically-inaccessible CCMs or significant medical comorbidities 3).

Shin et al. aimed to gain insight into the effect of SRS on CM and to propose possible mechanisms leading to recurrent hemorrhages following SRS.

During a 13-year interval between 2001 and 2013, bleeding recurred in 9 patients with CMs that had been treated using Gamma Knife surgery at the authors’ institution. Microsurgical removal was subsequently performed in 5 of these patients, who had recurrent hemorrhages between 4 months and 7 years after SRS. Specimens from 4 patients were available for analysis and used for this report.

Histopathological analysis demonstrated that vascular sclerosis develops as early as 4 months after SRS. In the samples from 2 to 7 years after SRS, sclerotic vessels were prominent, but there were also vessels with incomplete sclerosis as well as some foci of neovascularization.

Recurrent bleeding after SRS for CM could be related to incomplete sclerosis of the vessels, but neovascularization may also play a role 4).

From 1994 to 2001, 92 patients with 114 CMs were treated by GKS and then followed up for 2-8 years (mean 4.1+/-1.9). We analyzed the MRI features of CMs bleeding, efficacy of GKS, and the complications of treatment. Six pathological specimens after radiosurgery (1 from our group, 5 from other centers) were also assayed.

Among 43 patients who were treated by GKS to control their epilepsy, epileptic paroxysm was alleviated in 36 patients (83.7%), including 12 (27.9%) seizure-free. Rebleeding was confirmed in 9 patients (9.8%) by neuroimage, one of whom died. Transient symptomatic radiation edema occurred in 7 cases (7.6%) within 6-12 months after radiosurgery, and one patient underwent open surgery for cerebral decompression. The main pathological changes of cavernoma were coagulation necrosis and the vessels obliterated gradually after radiosurgery.

It is feasible to treat small and surgically high risk CMs by radiosurgery. The treatment has to be prudent in an acute bleeding and symptomatic progression. Optimal treatment timing and dose planning are prerequisites to reduce radiation-related complications. GKS is safe and effective to control the epilepsy caused by CMs, and also to bring down the rebleeding rate after a latency interval of several years 5).

Gamma knife radiosurgery for brainstem cavernous malformation.


Hu YJ, Zhang LF, Ding C, Tian Y, Chen J. Gamma Knife Radiosurgery for Cavernous Malformations of Basal Ganglia and Thalamus: A Retrospective Study of 53 Patients. Stereotact Funct Neurosurg. 2021 Jun 9:1-8. doi: 10.1159/000510108. Epub ahead of print. PMID: 34107485.

Wen R, Shi Y, Gao Y, Xu Y, Xiong B, Li D, Gong F, Wang W. The efficacy of gamma knife radiosurgery for cavernous malformation: a meta-analysis and review. World Neurosurg. 2018 Dec 21. pii: S1878-8750(18)32869-9. doi: 10.1016/j.wneu.2018.12.046. [Epub ahead of print] Review. PubMed PMID: 30583131.

Lee CC, Wang WH, Yang HC, Lin CJ, Wu HM, Lin YY, Hu YS, Chen CJ, Chen YW, Chou CC, Liu YT, Chung WY, Shiau CY, Guo WY, Hung-Chi Pan D, Hsu SPC. Gamma Knife radiosurgery for cerebral cavernous malformation. Sci Rep. 2019 Dec 24;9(1):19743. doi: 10.1038/s41598-019-56119-1. PMID: 31874979; PMCID: PMC6930272.

Shin SS, Murdoch G, Hamilton RL, Faraji AH, Kano H, Zwagerman NT, Gardner PA, Lunsford LD, Friedlander RM. Pathological response of cavernous malformations following radiosurgery. J Neurosurg. 2015 Oct;123(4):938-44. doi: 10.3171/2014.10.JNS14499. Epub 2015 Jun 19. PubMed PMID: 26090838.

Liu AL, Wang CC, Dai K. [Gamma knife radiosurgery for cavernous malformations]. Zhongguo Yi Xue Ke Xue Yuan Xue Bao. 2005 Feb;27(1):18-21. Chinese. PMID: 15782486.

Brainstem cavernous malformation approach

Brainstem cavernous malformation approach

The facial colliculus (FC), an important landmark for planning a surgical brainstem cavernous malformation approach (BCM), it may be difficult to identify on magnetic resonance imaging (MRI). Three-dimensional (3D) images may improve the FC-identification certainty; hence, a study attempted to validate the FC-identification certainty between two-dimensional (2D) and 3D images of patients with a normal brainstem and those with BCM. In this retrospective study, Uchida et al. included 10 patients with a normal brainstem and 10 patients who underwent surgery for BCM. The region of the FC in 2D and 3D images were independently identified by three neurosurgeons, three times in each case, using the method for continuously distributed test results (0-100). The intra- and inter-rater reliability of the identification certainty was confirmed using the intraclass correlation coefficient (ICC). The FC-identification certainty for 2D and 3D images was compared using the Wilcoxon signed-rank test. The ICC (1,3) and ICC (3,3) in both groups ranged from 0.88 to 0.99; therefore, the intra- and inter-rater reliability were good. In both groups, the FC-identification certainty was significantly higher for 3D images than for 2D images (normal brainstem group; 82.4 vs. 61.5, P = .0020, BCM group; 40.2 vs. 24.6, P = .0059 for the unaffected side, 29.3 vs. 17.3, P = .0020 for the affected side). In the normal brainstem and BCM groups, 3D images had better FC-identification certainty. 3D images are effective for the identification of the FC 1).

The anterior portion of mesencephalus and the interpeduncular fossa tissue may be accessed via subtemporal and retrosigmoidal approach to the posterior portion.

Supracerebellar infratentorial approach for brainstem cavernous malformation.

Lateral inferior cerebellar peduncle approach

Retrosigmoid approach

de Aguiar et al., preferred the retrosigmoid approach because it is more used due to the best view to the safety entry zones. 2).

Endoscopic endonasal surgery for a mesencephalic cavernoma 3).


Uchida T, Kin T, Koike T, Kiyofuji S, Uchikawa H, Takeda Y, Miyawaki S, Nakatomi H, Saito N. Identification of the Facial Colliculus in Two-dimensional and Three-dimensional Images. Neurol Med Chir (Tokyo). 2021 May 11. doi: 10.2176/nmc.oa.2020-0417. Epub ahead of print. PMID: 33980777.

de Aguiar PH, Zicarelli CA, Isolan G, Antunes A, Aires R, Georgeto SM, Tahara A, Haddad F. Brainstem cavernomas: a surgical challenge. Einstein (Sao Paulo). 2012 Jan-Mar;10(1):67-73. PubMed PMID: 23045829.

Enseñat J, d’Avella E, Tercero A, Valero R, Alobid I. Endoscopic endonasal surgery for a mesencephalic cavernoma. Acta Neurochir (Wien). 2014 Oct 24. [Epub ahead of print] PubMed PMID: 25342085.
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