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|LETTER TO THE EDITOR
|Year : 2013 | Volume
| Issue : 2 | Page : 189-191
Management issues in a complex case of basilar invagination associated with a large fourth ventricular dermoid and Klippel-Feil syndrome
Narayanam Anantha Sai Kiran1, Sunil Valentine Furtado1, Nandita Ghosal2, Alangar S Hegde1
1 Department of Neurosurgery, Sri Sathya Sai Institute of Higher Medical Sciences, Whitefield, Bangalore - 560 066, India
2 Department of Neuropathology, Sri Sathya Sai Institute of Higher Medical Sciences, Whitefield, Bangalore - 560 066, India
|Date of Submission||30-Nov-2012|
|Date of Decision||10-Dec-2012|
|Date of Acceptance||17-Mar-2013|
|Date of Web Publication||29-Apr-2013|
Narayanam Anantha Sai Kiran
Department of Neurosurgery, Sri Sathya Sai Institute of Higher Medical Sciences, Whitefield, Bangalore - 560 066
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Sai Kiran NA, Furtado SV, Ghosal N, Hegde AS. Management issues in a complex case of basilar invagination associated with a large fourth ventricular dermoid and Klippel-Feil syndrome. Neurol India 2013;61:189-91
|How to cite this URL:|
Sai Kiran NA, Furtado SV, Ghosal N, Hegde AS. Management issues in a complex case of basilar invagination associated with a large fourth ventricular dermoid and Klippel-Feil syndrome. Neurol India [serial online] 2013 [cited 2020 Dec 3];61:189-91. Available from: https://www.neurologyindia.com/text.asp?2013/61/2/189/111153
The association of a posterior fossa dermoid with congenital craniovertebral junction (CVJ) anomaly and Klippel - Feil syndrome is extremely uncommon. , We describe various surgical options in such patients and the rationale behind the approach chosen in the present case.
A 20-year-old male presented with restricted neck movements since childhood, progressive quadriparesis since six years, and bladder symptoms of a duration of six months. On examination, tone was increased in all four limbs with motor power of 4/5. The patient had a short neck with a low hairline. X-ray and computed tomography (CT) of CVJ [Figure 1]a-c revealed severe basilar invagination (BI) associated with cranial migration of C2 body to the region of the foramen magnum. There was associated platybasia, occipitalized posterior arch of C1, and fused C2-3 bodies. The odontoid tip was 20 mm above Chamberlain's line and 14 mm above McRae's line. The space available for the cord at the level of the foramen magnum was 3.4 mm [Figure 1]b. Magnetic resonance imaging (MRI) revealed a large fourth ventricular lesion extending from the region of foramen magnum to the posterior third ventricular and posterior interhemispheric regions [Figure 1]d-g. The lesion was hypo on T1- and hyper on T2-weighted images [Figure 1]d and e with restriction on diffusion weighted sequences [Figure 1]f and g.
|Figure 1: Preoperative images (a-g): CT (a-c) showing severe BI, thin C2 pedicles and deformed C1 lateral mass. MRI (d-g) showing fou rth ventricular lesion extending from foramen magnum to posterior t hird ventricular region. Postoperative images (h-o): Diffusion weighted MRI (h-j) after first surgery showing near total excision of the der moid. Intraoperative image (k) after posterior fusion showing b one graft lateral to titanium plates with no construct in midline (arrow). CT (l and m) and MRI (n) after T OO and posterior fusion showing no residual anterior compression. X-ray (o) showing titanium plates and sublaminar c ables|
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C1-C2 distraction and posterior fusion was considered technically not feasible as C1-C2 joints were quite anteriorly placed, C1 lateral mass was abnormal with no significant bone for C1 lateral mass screw placement, and C2 pedicles were extremely thin [Figure 1]c. The only option for BI was transoral odontoidectomy (TOO) and posterior fusion. It was considered extremely difficult to excise the posterior fossa lesion completely by a limited midline suboccipital craniectomy, as the lesion extended quite superiorly close to the internal cerebral veins [Figure 1]e. Hence, excision of the posterior fossa lesion by occipital transtentorial approach (Poppen's approach) was planned initially. The aim of the initial occipital transtentorial approach was complete excision of the interhemispheric and posterior third ventricular components along with fourth ventricular component from above to the extent possible, so that any residual inferior part could be excised during subsequent surgery (posterior fusion) by a limited suboccipital craniectomy.
After fiber-optic - aided intubation, the patient was positioned in a prone position with the neck in a neutral position with no flexion, extension, and rotation, and the head fixed in a three-pin fixator for an occipital transtentorial approach to the posterior fossa lesion. The tentorium cerebelli was widely sectioned. The lesion was pearly white with hair inside. A near-total excision of the lesion was done with endoscopic assistance. Histopathology of the posterior fossa lesion was suggestive of a dermoid. MR imaging after this surgery revealed near-total excision of the posterior fossa lesion [Figure 1]h-j. TOO and posterior fusion was done two months after the initial surgery. The odontoid process and C2 body in midline were removed. Occipitocervical fusion was done with two separate laterally placed titanium plates with holes and sublaminar titanium cables. Bone graft was placed on either side lateral to the titanium plates extending from the occiput to C2 [Figure 1]k. The titanium plates were positioned as laterally as possible and the midline suboocipital bone was not used for bony fusion so as to deal with any recurrence of the posterior fossa lesion in the future, without disturbing the construct used for the posterior fusion. Postoperative CT and MRI done at the time of discharge revealed no residual anterior compression [Figure 1]l-n. At a final follow-up after eight months, power in all four limbs of the patient had improved to 4+/5 and his bladder symptoms had completely subsided.
Dermoids are derived from the ectopic inclusion of epithelial cells due to the failure of cleavage of the neuroectoderm from the cutaneous ectoderm during closure of neural tubes. ,,, Failure of formation and rearrangement of cervical sclerotomes results in Klippel - Feil syndrome. ,,, The embryological basis of BI is more complex and probably results from a failure of correction of physiological BI during the course of fetal development. , The exact embryological basis for the association of congenital CVJ anomalies and Klippe - Feil syndrome with dermoid is not clear and various hypotheses involving the underexpression of the Pax genes, altered tissue tension due to shortening of the cervical spine during the formation of cephalic and cervical flexures, reduced fetal movements, and so on have been proposed. ,,, In patients with this rare association, excision of the posterior fossa lesion through a limited suboccipital craniectomy with endoscopic assistance followed by occipitocervical fusion has been reported. , However, these lesions were close to the foramen magnum unlike in the present case, in which the lesion could not be excised completely by such limited craniectomy. The rationale behind excision of the posterior fossa lesion by the occipital transtentorial approach initially in our case was to preserve the suboccipital bone to the maximum extent possible by removing the lesion as much as possible from above. Excision of the posterior fossa lesion with endoscopic assistance helps in preserving the suboccipital bone in these patients.
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