Long-term imaging course of Chiari malformation type I due to fibrous dysplasia/McCune-Albright syndrome

INTRODUCTION

McCune-Albright syndrome (MAS) and fibrous dysplasia (FD) have been reported to cause Chiari type I malformation (CM1) and skull base invagination (BI).

CASE

A 6-year-old girl was diagnosed with MAS and FD. She was diagnosed with CM1 at age 8 years, and the syringomyelia had gradually increased by age 20 years. We performed foramen magnum decompression and C1 laminectomy, and the syringomyelia stopped spreading after surgery.

DISCUSSION

This patient underwent long-term radiological observation and morphological evaluations, which revealed that the skull thickening was progressing, while the posterior cranial fossa volume (PCFV) remained unchanged for 14 years. Therefore, although PCFV did not decrease, it was considered to be relatively inadequate due to the increase in brain volume with growth, resulting in posterior fossa overcrowding, causing CM1.

CONCLUSION

In patients with FD/MAS, long-term evaluation of bone thickening, odontoid position, and PCFV is necessary.

Tonsillectomy with modified reconstruction of the cisterna magna with and without craniectomy for the treatment of adult Chiari malformation type I with syringomyelia

BACKGROUND

In light of the controversies regarding the surgical treatment of adult Chiari malformation type I (CM-I) with syringomyelia, a retrospective study was conducted to evaluate the safety and efficacy of tonsillectomy followed by modified reconstruction of the cisterna magna with or without craniectomy.

METHODS

Between 2008 and 2017, 78 adult CM-I patients (36 males and 42 females, mean age 40.6 years old) with syringomyelia were treated with posterior fossa decompression (PFD) with tonsillectomy and modified reconstruction of the cisterna magna. Patients were divided into two study groups: group A (n = 40) underwent cranioplasty with replacement of the bone flap; group B (n = 38) underwent suboccipital craniectomy. Neurological outcomes were evaluated by traditional physician assessment (improved, unchanged, and worsened) and the Chicago Chiari Outcome Scale (CCOS). Syringomyelia outcomes were assessed radiologically.

RESULTS

The procedure was successfully performed in all patients, and restoration of normal cerebrospinal fluid (CSF) flow was confirmed by intraoperative ultrasonography. The median postoperative follow-up was 20.3 months (range 18-60 months). Clinical improvement was evident in 66 (84.6%) patients, with no significant differences between the two groups (85.0% vs. 84.2%, P = 0.897). According to the CCOS, 36 patients (90.0%) in group A were labeled as "good" outcome, compared with that of 34 (86.8%) in group B (P = 0.734). Improvement of syringomyelia was also comparable between the groups, which was observed in 35 (87.5%) vs. 33 (86.8%) patients (P = 0.887). The postoperative overall (7.5% vs. 23.7%, P = 0.048) and CSF-related (2.5% vs. 18.4%, P = 0.027) complication rates were significantly lower in group A than group B.

CONCLUSIONS

Tonsillectomy with modified reconstruction of the cisterna magna without craniectomy seems to be a safe and effective surgical option to treat adult CM-I patients with syringomyelia, though future well-powered prospective randomized studies are warranted to validate these findings.

Cystic Degeneration of Cerebellar Tonsil 1 Year After Chiari I Malformation Surgery: A Case Report and Review of the Literature

BACKGROUND

Chiari malformation results from a bony structural anomaly of the skull base. The structural defect causes downward displacement of the cerebellar tonsils through the foramen magnum. The herniated tonsils block the normal flow of cerebrospinal fluid, which causes a wide spectrum of clinical symptoms.

CASE REPORT

In May 2015, a 16-year-old girl was referred to our center because of a 1-year history of occipital headache, most often triggered by exercise and physical activity at school. She had experienced new-onset numbness in both hands, more severe on the right side, associated with some degrees of weakness. Eventually, an evaluation of her condition included magnetic resonance imaging in T1 and T2 sequences, which revealed a 20-mm downward migration of the cerebellar tonsils, associated with a cervical cord syrinx at the level of the fourth and fifth cervical vertebrae. The patient underwent posterior fossa decompression and C1 and partial C2 laminectomies. Postoperatively there were no complications, and the patient was discharged on day 3. Postoperatively, she experienced some improvement in her symptoms. After 2 months of routine outpatient follow-up, she was better, the headaches had subsided, she could resume some activities, and there was no paresis in her limbs.

CONCLUSIONS

In cases of progressive symptoms of Chiari malformation, surgical decompression is important and should be considered after shunt insertion to the hindbrain.

Cerebellar tonsil ectopia measurement in type I Chiari malformation patients show poor inter-operator reliability

Background

Type 1 Chiari malformation (CM-I) has been historically defined by cerebellar tonsillar position (TP) greater than 3–5 mm below the foramen magnum (FM). Often, the radiographic findings are highly variable, which may influence the clinical course and patient outcome. In this study, we evaluate the inter-operator reliability (reproducibility) of MRI-based measurement of TP in CM-I patients and healthy controls.

Methods

Thirty-three T2-weighted MRI sets were obtained for 23 CM-I patients (11 symptomatic and 12 asymptomatic) and 10 healthy controls. TP inferior to the FM was measured in the mid-sagittal plane by seven expert operators with reference to McRae’s line. Overall agreement between the operators was quantified by intraclass correlation coefficient (ICC).

Results

The mean and standard deviation of cerebellar TP measurements for asymptomatic (CM-Ia) and symptomatic (CM-Is) patients in mid-sagittal plane was 6.38 ± 2.19 and 9.57 ± 2.63 mm, respectively. TP measurements for healthy controls was 0.48 ± 2.88 mm. The average range of TP measurements for all data sets analyzed was 7.7 mm. Overall operator agreement for TP measurements was relatively high with an ICC of 0.83.

Conclusion

The results demonstrated a large average range (7.7 mm) of measurements among the seven expert operators and support that, if economically feasible, two radiologists should make independent measurements before radiologic diagnosis of CM-I and surgery is contemplated. In the future, an objective diagnostic parameter for CM-I that utilizes automated algorithms and results in smaller inter-operator variation may improve patient selection.

The Tonsillouvular Fissure Approach: Access to Dorsal and Lateral Aspects of the Fourth Ventricle

OBJECTIVE

Although approaches to the fourth ventricle (FV) have been studied well, approaches to the lesions located in the dorsal and lateral aspects of the FV have not been shown in anatomic or clinical studies. The aim of this study is to show for the first time in the literature the tonsillouvular fissure approach (TUFA) in anatomic dissections and its use in surgical series.

METHODS

For anatomic studies, 4 formalin-fixed human cadaveric heads infused with colored silicone and 10 cerebellar specimens were dissected in a stepwise manner. Records of 12 patients operated on via TUFA were also retrospectively reviewed.

RESULTS

Neurosurgical anatomy and critical steps of TUFA were described in detail. Among 12 patients with lesions around the FV (4 cavernous malformation, 2 pilocytic astrocytoma, 2 hemangioblastoma, 1 B-cell lymphoma, 1 metastatic papillary carcinoma, 1 dermoid cyst, and 1 arteriovenous malformation), 11 gross total and 1 subtotal resection were achieved via TUFA without any mortality or morbidity. Comparative analyses of 4 surgical approaches to FV (TUFA, telovelar/cerebellomedullary fissure, supratonsillar/tonsillobiventral lobule fissure, and transvermian approaches) were also presented.

CONCLUSIONS

TUFA provides a direct route and excellent surgical view to lesions around the FV, particularly on dorsal and lateral aspects, inferior vermis, and medial part of the dentate nucleus and cerebellar peduncles. It minimizes traversing the normal cerebellar tissue compared with a transvermian approach.

Delineating function and connectivity of optokinetic hubs in the cerebellum and the brainstem

Optokinetic eye movements are crucial for keeping a stable image on the retina during movements of the head. These eye movements can be differentiated into a cortically generated response (optokinetic look nystagmus) and the highly reflexive optokinetic stare nystagmus, which is controlled by circuits in the brainstem and cerebellum. The contributions of these infratentorial networks and their functional connectivity with the cortical eye fields are still poorly understood in humans. To map ocular motor centres in the cerebellum and brainstem, we studied stare nystagmus using small-field optokinetic stimuli in the horizontal and vertical directions in 22 healthy subjects. We were able to differentiate ocular motor areas of the pontine brainstem and midbrain in vivo for the first time. Direction and velocity-dependent activations were found in the pontine brainstem (nucleus reticularis, tegmenti pontis, and paramedian pontine reticular formation), the uvula, flocculus, and cerebellar tonsils. The ocular motor vermis, on the other hand, responded to constant and accelerating velocity stimulation. Moreover, deactivation patterns depict a governing role for the cerebellar tonsils in ocular motor control. Functional connectivity results of these hubs reveal the close integration of cortico-cerebellar ocular motor and vestibular networks in humans. Adding to the cortical concept of a right-hemispheric predominance for visual-spatial processing, we found a complementary left-sided cerebellar dominance for our ocular motor task. A deeper understanding of the role of the cerebellum and especially the cerebellar tonsils for eye movement control in a clinical context seems vitally important and is now feasible with functional neuroimaging.