Position Of Cerebellar Tonsils Research Articles

Occipital artery-posterior inferior cerebellar artery bypass: a cadaveric feasibility study

PurposeTo demonstrate that occipital artery (OA)-p1 posterior inferior cerebellar artery (PICA) bypass can be an alternative for complex posterior circulation aneurysms.MethodsA far-lateral approach to craniotomy was performed on 20 cadaveric specimens, and the OA was obtained 'in-line.' Its length, diameter, and the number of p1/p2 and p3 segmental perforators were determined, and the relationship between the caudal loop and cerebellar tonsil position was also assessed. The distance between the PICA’s origin and the cranial nerve XI (CN XI), the buffer length above the CN XI after dissection, the OA length required to complete the OA-p1/p3 PICA bypass, and the p1 and p3 segment diameters were all measured. A bypass training practical scale (TSIO) was used to evaluate the quality of the anastomosis.ResultsAll specimens underwent OA-p1 PICA end-to-end bypass and had favorable results for the TSIO score, 15 sides underwent OA-p3 PICA end-to-side bypass, and the other bypass protocols were less common. The buffer length above the CN XI after dissection, the distance between the PICA’s origin and the CN XI, and the first perforator were all of sufficient length. The direct length of the OA needed to complete the OA-p1 PICA end-to-end bypass was significantly less than the available length and the OA-p3 PICA end-to-side bypass, with the OA matching the p1 segment diameter. The number of p1 perforators was less than that of p3, and the OA diameter was equal to that of the p1 segment.ConclusionOA-p1 PICA end-to-end bypass is a feasible alternative in cases in which p3 segment has high caudal loops or anatomic anomalies.

Effects of age and gender on posterior cranial fossa linear volume and cerebellar tonsil position in normal populations

To investigate the effects of gender and age on the posterior cranial fossa linear volume and cerebellar tonsil position in normal populations. A total of 180 normal adults who underwent cervical MRI examination at the physical examination center were selected, including 90 males and 90 females; the age ranged from 20 to 79 years, with an average of 50.4 years. The posterior cranial fossa linear volume and cerebellar tonsil position were measured by two spine surgeons on the mid-sagittal plane of the cervical MRI T2-weighted image. The posterior cranial fossa linear volume included the length of clivus (AB), anteroposterior diameter of foramen magnum (BC), length of supraocciput (CD), anteroposterior diameter of posterior fossa (DA), posterior fossa height (BE), and clivus angle (∠α). The index of the cerebellar tonsil position was the distance from the lower edge of the cerebellar tonsil to the baseline (MN). The differences of each indicators between males and females were compared, and the correlations between age and each indicators were analyzed. The posterior fossa cranial linear volume AB, BC, CD, BE, and ∠α in males were significantly larger than those in females ( P<0.05); DA in males was larger than that in females, but showing no significant difference ( t=1.978, P=0.050). The cerebellar tonsil position (MN) in females was higher than that in males, but showing no significant difference ( t=0.526, P=0.600). Correlation analysis showed that age was negatively correlated with AB, BC, CD, DA, BE, ∠α, and MN ( r=-0.375, P=0.001; r=-0.417, P=0.001; r=-0.046, P=0.001; r=-0.244, P=0.001; r=-0.326, P=0.001; r=-0.320, P=0.001; r=-0.334, P=0.001). The posterior cranial fossa linear volume of normal adults is significantly larger in males than in females; the posterior cranial fossa linear volume and the cerebellar tonsil position may have a decreasing process of age-related degeneration.

Signs of Intracranial Hypertension, Hypermobility, and Craniocervical Obstructions in Patients With Myalgic Encephalomyelitis/Chronic Fatigue Syndrome

The pathophysiology of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is unknown. In this study, we test the hypothesis that hypermobility, signs of intracranial hypertension (IH), and craniocervical obstructions may be overrepresented in patients with ME/CFS and thereby explain many of the symptoms. Our study is a retrospective, cross-sectional study, performed at a specialist clinic for referred patients with severe ME/CFS as defined by the Canada Consensus Criteria. The first 272 patients with ME/CFS were invited to participate, and 229 who provided prompt informed consent were included. Hypermobility was assessed using the Beighton Score. IH was assessed indirectly by the quotient of the optic nerve sheet diameter (ONSD)/eyeball transverse diameter on both sides as measured on magnetic resonance imaging (MRI) of the brain. We also included assessment of cerebellar tonsil position in relation to the McRae line, indicating foramen magnum. Craniocervical obstructions were assessed on MRI of the cervical spine. Allodynia was assessed by quantitative sensory testing (QST) for pain in the 18 areas indicative of fibromyalgia syndrome (FMS). A total of 190 women, mean age 45 years, and 39 males, mean age 44 years, were included. Hypermobility was identified in 115 (50%) participants. MRI of the brain was performed on 205 participants of whom 112 (55%) had an increased ONSD and 171 (83%) had signs of possible IH, including 65 (32%) who had values indicating more severe states of IH. Cerebellar tonsils protruding under the McRae line into the foramen magnum were identified in 115 (56%) of the participants. MRI of the cervical spine was performed on 125 participants of whom 100 (80%) had craniocervical obstructions. Pain at harmless pressure, allodynia, was found in 96% of the participants, and FMS was present in 173 participants or 76%. Compared to a general population, we found a large overrepresentation of hypermobility, signs of IH, and craniocervical obstructions. Our hypothesis was strengthened for future studies on the possible relation between ME/CFS symptoms and hypermobility, IH, and craniocervical obstructions in a portion of patients with ME/CFS. If our findings are confirmed, new diagnostic and therapeutic approaches to this widespread neurological syndrome should be considered.

The Filum disease and the Neuro-Cranio-vertebral syndrome: definition, clinical picture and imaging features

BackgroundWe propose two new concepts, the Filum Disease (FD) and the Neuro-cranio-vertebral syndrome (NCVS), that group together conditions thus far considered idiopathic, such as Arnold-Chiari Syndrome Type I (ACSI), Idiopathic Syringomyelia (ISM), Idiopathic Scoliosis (IS), Basilar Impression (BI), Platybasia (PTB) Retroflexed Odontoid (RO) and Brainstem Kinking (BSK).MethodWe describe the symptomatology, the clinical course and the neurological signs of the new nosological entities as well as the changes visible on imaging studies in a series of 373 patients.ResultsOur series included 72% women with a mean age of 33.66 years; 48% of the patients had an interval from onset to diagnosis longer than 10 years and 64% had a progressive clinical course. The commonest symptoms were: headache 84%, lumbosacral pain 72%, cervical pain 72%, balance alteration 72% and paresthesias 70%. The commonest neurological signs were: altered deep tendon reflexes in upper extremities 86%, altered deep tendon reflexes in lower extremities 82%, altered plantar reflexes 73%, decreased grip strength 70%, altered sensibility to temperature 69%, altered abdominal reflexes 68%, positive Mingazzini’s test 66%, altered sensibility to touch 65% and deviation of the uvula and/or tongue 64%. The imaging features most often seen were: altered position of cerebellar tonsils 93%, low-lying Conus medullaris below the T12L1 disc 88%, idiopathic scoliosis 76%, multiple disc disease 72% and syringomyelic cavities 52%.ConclusionsThis is a paradigm shift that opens up new paths for research and broadens the range of therapeutics available to these patients.

Treatment analysis of craniosynostosis combined with Chiari malformation in children

Objective To explore the surgical method and outcome of craniosynostosis combined with Chiari malformation in children. Methods A retrospective analysis was conducted on the clinical data of 16 children with craniosynostosis combined with Chiari malformation who were admitted to Department of Neurosurgery, Children′s Hospital of Nanjing Medical University from April to December 2017. All cases were retrospectively analyzed and their imaging results were analyzed. Of the 16 children without hydrocephalus, 12 underwent craniofacial reconstruction of cranial suture or craniofacial reconstruction, of which 1 case underwent posterior fossa reconstruction and suboccipital decompression at 7 months post operation. In 4 children with combined hydrocephalus, 3 underwent routine right ventricle-peritoneal shunting and cranial reconstruction, of which 1 case was treated with posterior fossa reconstruction and suboccipital decompression at 5 months post operation. The other 1 case was Pfeiffer syndrome and underwent right ventricle-peritoneal shunting plus posterior fossa reconstruction as well as suboccipital decompression. At 3, 6 and 12 months post operation, all patients were followed up at the outpatient clinic and underwent the reexamination of head MRI for assessment of brain tissue development, ventricle changes and cerebellum tonsil herniation. Results All 16 children underwent operation successfully without any surgical complications. Revealed by the postoperative skull CT, all the children′s cranial cavity volume was enlarged, and the cranial malformation was improved. The follow-up time of 16 children was (12.1±2.0) months (10-18 months). The review of head MRI showed that brain tissue developed well and the position of the cerebellar tonsils did not decline further. All children were free of neurological deficits, and parents were satisfied with the improvement in the appearance of their skulls and faces. Conclusions The combination of craniosynostosis with Chiari malformation should be fully evaluated before surgery and appropriate individualized treatment program should be selected according to specific conditions. One-stage craniofacial surgery seems an effective treatment method. Key words: Craniosynostosis; Arnold-Chiari malformation; Child; Treatment outcome

S1-02 SESSION 1: NEUROSURGERY INTRACRANIAL HYPERTENSION AND CORTICAL THICKNESS IN SYNDROMIC CRANIOSYNOSTOSIS

Introduction: Intracranial hypertension (ICH) is a frequent indication for surgical intervention in syndromic craniosynostosis. Various clinical risk factors have been described, but potential effects on underlying brain morphology have not been investigated. This study seeks to evaluate the impact of ICH risk factors on cerebral cortex thickness in syndromic craniosynostosis. Methods: Patient records and imaging were reviewed for ICH risk factors and demographic data including papilledema, hydrocephalus, moderate to severe obstructive sleep apnea, cerebellar tonsillar position, occipitofrontal circumference curve deflection, age at the time of scan, and sex in 107 syndromic (Apert, Crouzon, Pfeiffer, Muenke, Saethre-Chotzen) craniosynostosis patients. 171 MRI scans of these patients were then analyzed. Average cortical thickness estimates were obtained via an auto-segmentation/ auto-parcellation image processing software (FreeSurfer) and exported for statistical analysis. A linear mixed effects model accounting for repeated measurements, age, gender, and syndrome influences was developed to determine impact of ICH risk factors on cerebral cortex thickness changes (significance p < .05). Results: Average cortical thickness in this cohort was 2.78 ± 0.17 mm with an average age of 8.88 years (range 1.15 – 34.03) at the time of scan. Cortical thickness did not vary significantly by sex (p = 0.534) or syndrome (p = 0.896) as independent predictors. A history of papilledema (p = .036) or hydrocephalus (p = .007) prior to scan date was associated with thinner cortices than those without. Average cortical thickness was also shown to significantly vary with the age of the patient at the time of MRI (p < 0.001), with older patients having thinner cortices. History of moderate to severe obstructive sleep apnea (oAHI > 5) (p = .464), cerebellar tonsil position (p = .682), or history of occipitofrontal circumference curve deflection (p = .375) prior to scan date did not result in significant cortical thickness changes. Conclusions: Our results indicate that a history of hydrocephalus or papilledema results in a thinner cerebral cortex on average in syndromic craniosynostosis patients. This suggests structural consequences from the development of intracranial hypertension and may support early intervention to avoid such effects. Further investigation is needed to evaluate the link between these findings, timing of intervention, and neuropsychological development.

Intracranial Hypertension and Cortical Thickness in Syndromic Craniosynostosis

INTRODUCTION: Intracranial hypertension (ICH) is a frequent indication for surgical intervention in syndromic craniosynostosis. Various clinical risk factors have been described, but potential effects on underlying brain morphology have not been investigated. This study seeks to evaluate the impact of ICH risk factors on cerebral cortex thickness in syndromic craniosynostosis. METHODS: Patient records and imaging were reviewed for ICH risk factors and demographic data including papilledema, hydrocephalus, moderate to severe obstructive sleep apnea, cerebellar tonsillar position, occipitofrontal circumference curve deflection, age at the time of scan, and sex in 107 syndromic (Apert, Crouzon, Pfeiffer, Muenke, Saethre-Chotzen) craniosynostosis patients. One hundred seventy-one magnetic resonance imaging scans of these patients were then analyzed. Average cortical thickness estimates were obtained via an auto-segmentation/auto-parcellation image processing software (FreeSurfer) and exported for statistical analysis. A linear mixed-effect model accounting for repeated measurements, age, gender, and syndrome influences was developed to determine impact of ICH risk factors on cerebral cortex thickness changes (significance P < 0.05). RESULTS: Average cortical thickness in this cohort was 2.78 ± 0.17 mm with an average age of 8.88 years (range, 1.15–34.03) at the time of scan. Cortical thickness did not vary significantly by sex (P = 0.534) or syndrome (P = 0.896) as independent predictors. A history of papilledema (P = 0.036) or hydrocephalus (P = 0.007) before scan date was associated with thinner cortices than those without. Average cortical thickness was also shown to significantly vary with the age of the patient at the time of magnetic resonance imaging (P < 0.001), with older patients having thinner cortices. History of moderate to severe obstructive sleep apnea (oAHI > 5) (P = 0.464), cerebellar tonsil position (P = 0.682), or history of occipitofrontal circumference curve deflection (P = 0.375) before scan date did not result in significant cortical thickness changes. CONCLUSIONS: Our results indicate that a history of hydrocephalus or papilledema results in a thinner cerebral cortex on average in syndromic craniosynostosis patients. This suggests structural consequences from the development of ICH and may support early intervention to avoid such effects. Further investigation is needed to evaluate the link between these findings, timing of intervention, and neuropsychological development.

Morphometric and volumetric comparison of 102 children with symptomatic and asymptomatic Chiari malformation Type I.

OBJECTIVE Chiari malformation Type I (CM-I) is typically defined on imaging by a cerebellar tonsil position ≥ 5 mm below the foramen magnum. Low cerebellar tonsil position is a frequent incidental finding on brain or cervical spine imaging, even in asymptomatic individuals. Nonspecific symptoms (e.g., headache and neck pain) are common in those with low tonsil position as well as in those with normal tonsil position, leading to uncertainty regarding appropriate management for many patients with low tonsil position and nonspecific symptoms. Because cerebellar tonsil position is not strictly correlated with the presence of typical CM-I symptoms, the authors sought to determine if other 2D morphometric or 3D volumetric measurements on MRI could distinguish between patients with asymptomatic and symptomatic CM-I. METHODS The authors retrospectively analyzed records of 102 pediatric patients whose records were in the University of Michigan clinical CM-I database. All patients in this database had cerebellar tonsil position ≥ 5 mm below the foramen magnum. Fifty-one symptomatic and 51 asymptomatic patients were matched for age at diagnosis, sex, tonsil position, and tonsil morphology. National Institutes of Health ImageJ software was used to obtain six 2D anatomical MRI measurements, and a semiautomated segmentation tool was used to obtain four 3D volumetric measurements of the posterior fossa and CSF subvolumes on MRI. RESULTS No significant differences were observed between patients with symptomatic and asymptomatic CM-I related to tentorium length (50.3 vs 51.0 mm; p = 0.537), supraoccipital length (39.4 vs 42.6 mm; p = 0.055), clivus-tentorium distance (52.0 vs 52.1 mm; p = 0.964), clivus-torcula distance (81.5 vs 83.3 mm; p = 0.257), total posterior fossa volume (PFV; 183.4 vs 190.6 ml; p = 0.250), caudal PFV (152.5 vs 159.8 ml; p = 0.256), fourth ventricle volume to caudal PFV ratio (0.0140 vs 0.0136; p = 0.649), or CSF volume to caudal PFV ratio (0.071 vs 0.061; p = 0.138). CONCLUSIONS No clinically useful 2D or 3D measurements were identified that could reliably distinguish pediatric patients with symptoms attributable to CM-I from those with asymptomatic CM-I.

313 Morphometric and Volumetric Comparison of Symptomatic and Asymptomatic Chiari Malformation Type I

Abstract INTRODUCTION Chiari malformation type I (CMI) is typically defined by a cerebellar tonsil position 5 mm or more below foramen magnum. Low cerebellar tonsil position is a frequent incidental finding, even in asymptomatic individuals. Non-specific symptoms such as headache and neck pain are common in those with low tonsil position and in those with normal tonsil position, leading to uncertainty regarding appropriate management for many patients with low tonsil position and non-specific symptoms. Since cerebellar tonsil position is not strictly correlated with typical CMI symptoms, we sought to determine if other 2D morphometric or 3D volumetric measurements on MRI could distinguish asymptomatic from symptomatic CMI patients. METHODS We retrospectively analyzed 102 pediatric patients from the University of Michigan clinical CMI database. All patients in this database have cerebellar tonsil position at least 5 mm below foramen magnum. Fifty-one symptomatic and 51 asymptomatic patients were matched for age at diagnosis, sex, tonsil position, and tonsil morphology. Five 2D anatomic MRI measurements and four 3D volumetric measurements of posterior fossa and CSF sub-volumes on MRI were measured. RESULTS &gt;There were no significant differences observed between symptomatic and asymptomatic CMI patients related to basilar impression (−5.9 mm vs. −7.0 mm; P = 0.026), tentorium length (50.3 mm vs. 51.0 mm; P = 0.537), supraoccipital length (39.4 mm vs. 42.6 mm; P = 0.055), clivus-tentorium distance (52.0 mm vs. 52.1 mm; P = 0.964), clivus-torcula distance (81.5 mm vs. 83.3 mm; P = 0.257), total posterior fossa volume (PFV; 183.4 mL vs. 190.6 mL; P = 0.250), caudal PFV (152.5 mL vs. 159.8 mL; P = 0.256), fourth ventricle volume to caudal PFV ratio (0.0140 vs. 0.0136; P = 0.649), or CSF volume to caudal PFV ratio (0.071 vs. 0.061; P = 0.138). CONCLUSION We did not identify any 2D or 3D measurements that could reliably distinguish pediatric patients with symptoms attributable to CMI from those with asymptomatic CMI.

Syrinx location and size according to etiology: identification of Chiari-associated syrinx.

OBJECT Syrinx size and location within the spinal cord may differ based on etiology or associated conditions of the brain and spine. These differences have not been clearly defined. METHODS All patients with a syrinx were identified from 14,118 patients undergoing brain or cervical spine imaging at a single institution over an 11-year interval. Syrinx width, length, and location in the spinal cord were recorded. Patients were grouped according to associated brain and spine conditions including Chiari malformation Type I (CM-I), secondary CM (2°CM), Chiari malformation Type 0 (CM-0), tethered cord, other closed dysraphism, and spinal tumors. Syringes not associated with any known brain or spinal cord condition were considered idiopathic. Syrinx characteristics were compared between groups. RESULTS A total of 271 patients with a syrinx were identified. The most common associated condition was CM-I (occurring in 117 patients [43.2%]), followed by spinal dysraphism (20 [7.4%]), tumor (15 [5.5%]), and tethered cord (13 [4.8%]). Eighty-three patients (30.6%) did not have any associated condition of the brain or spinal cord and their syringes were considered idiopathic. Syringes in patients with CM-I were wide (7.8 ± 3.9 mm) compared with idiopathic syringes (3.9 ± 1.0, p < 0.0001) and those associated with tethered cord (4.2 ± 0.9, p < 0.01). When considering CM-I-associated and idiopathic syringes, the authors found that CM-I-associated syringes were more likely to have their cranial extent in the cervical spine (88%), compared with idiopathic syringes (43%; p < 0.0001). The combination of syrinx width greater than 5 mm and cranial extent in the cervical spine had 99% specificity (95% CI 0.92-0.99) for CM-I-associated syrinx. CONCLUSIONS Syrinx morphology differs according to syrinx etiology. The combination of width greater than 5 mm and cranial extent in the cervical spine is highly specific for CM-I-associated syringes. This may have relevance when determining the clinical significance of syringes in patients with low cerebellar tonsil position.

The association between Chiari malformation Type I, spinal syrinx, and scoliosis.

OBJECT Chiari malformation Type I (CM-I) is often found in patients with scoliosis. Most previous reports of CM-I and scoliosis have focused on patients with CM-I and a spinal syrinx. The relationship between CM-I and scoliosis in the absence of a syrinx has never been defined clearly. The authors sought to determine if there is an independent association between CM-I and scoliosis when controlling for syrinx status. METHODS The medical records of 14,118 consecutive patients aged ≤ 18 years who underwent brain or cervical spine MRI at a single institution in an 11-year span were reviewed to identify patients with CM-I, scoliosis, and/or syrinx. The relationship between CM-I and scoliosis was analyzed by using multivariate regression analysis and controlling for age, sex, CM-I status, and syrinx status. RESULTS In this cohort, 509 patients had CM-I, 1740 patients had scoliosis, and 243 patients had a spinal syrinx. The presence of CM-I, the presence of syrinx, older age, and female sex were each significantly associated with scoliosis in the univariate analysis. In the multivariate regression analysis, older age (OR 1.02 [95% CI 1.01-1.03]; p < 0.0001), female sex (OR 1.71 [95% CI 1.54-1.90]; p < 0.0001), and syrinx (OR 9.08 [95% CI 6.82-12.10]; p < 0.0001) were each independently associated with scoliosis. CM-I was not independently associated with scoliosis when controlling for these other variables (OR 0.99 [95% CI 0.79-1.29]; p = 0.9). CONCLUSIONS A syrinx was independently associated with scoliosis in a large pediatric population undergoing MRI. CM-I was not independently associated with scoliosis when controlling for age, sex, and syrinx status. Because CM-I is not independently associated with scoliosis, scoliosis should not necessarily be considered a symptom of low cerebellar tonsil position in patients without a syrinx.

Effect of upright posture on tonsillar level in adolescent idiopathic scoliosis

Results In AIS patients, the cerebellar tonsil position was significantly lower in the upright than the supine position (-0.7 +/-1.5 vs +1.2+/-1.7, p<0.00001) while in normal subjects, there was no change in cerebellar tonsil position between upright and supine positions (mean +2.1+/-1.7 vs +2.2 +/-1.8, p = 0.93). AIS patients also had a greater degree of tonsillar excursion between upright and supine positions compared to normal subjects (mean -1.9 +/-1.6 vs -0.1 +/-1.7, p<0.00001). More AIS patients tended to have tonsillar descent in the upright position rather than the supine position though this did not reach statistical significance (28% in supine position vs 48% in standing position, p=0.15). There is slightly better correlation between tonsillar level and Cobb angle in upright position (r = 0.45, p = 0.01) than those in supine position (r= 0.31, p=0.03) in AIS patients. Conclusion AIS patients have more tonsillar descent in the upright position and a greater degree of tonsillar excursion between supine and upright positions compared to matched control subjects. Apart from supporting the hypothesis of relative cord tethering in AIS, the results also enhance the likelihood of more significant chronic dynamic compression of the brainstem and upper cervical cord in AIS. Whether this will lead to chronic insult with subclinical neurophysiological disturbance, affecting both dynamic postural balance and SSEP, and contributing to the etiopathogenesis of AIS, warrants further study.

Results of posterior cranial vault remodeling for plagiocephaly and brachycephaly by the meander technique.

Several techniques to remodel the posterior calvarium in order to increase intracranial volume (ICV) and to improve cosmetic appearance are reported. This study presents the results of meander technique in patients with brachycephaly and posterior plagiocephaly. During December 2011 and July 2013, a total of 12 children (median age: 15 months) underwent posterior cranial vault remodeling by the meander technique (brachycephaly, n = 6; posterior plagiocephaly, n = 6). The available pre- and postoperative MRIs were assessed with regard to ICV, cranial index (CI) and asymmetry index (AI) as well as the position of the cerebellar tonsils. No intra- or postoperative complications were observed. Blood transfusions were necessary in nine of 12 patients. A significant increase of the ICV from 1,178.4 ± 134.5 to 1,293.0 ± 137.5 cm(3) (p < 0.05) is demonstrated. In the patients with brachycephaly the CI was significantly improved from 0.97 ± 0.12 to 0.89 ± 0.12 postoperatively (p < 0.05). The AI in patients with posterior plagiocephaly was significantly ameliorated from 0.83 ± 0.04 to 0.92 ± 0.02 postoperatively (p < 0.05). There was a significant effect on cerebellar tonsil position in relation to foramen magnum level for patients with brachycephaly (right tonsil: 11.9 ± 9.2 to 7.0 ± 9.1 mm, p < 0.05; left: 10.8 ± 9.5 to 9.7 ± 10.6 mm; p < 0.05) as well as in posterior plagiocephaly for the ipsilateral tonsil (3.2 ± 3.5 to 1.6 ± 3.5 mm; p < 0.01). The presented surgical technique is considered to be safe. The technique is capable to significantly increase ICV and improve cosmetic appearance of the remodeled calvarium. Further evidence that posterior cranial vault remodeling influences the position of the cerebellar tonsils is added by the results of the study.

Distribution of cerebellar tonsil position: implications for understanding Chiari malformation

Prior attempts to define normal cerebellar tonsil position have been limited by small numbers of patients precluding analysis of normal distribution by age group. The authors' objective in the present study was to analyze cerebellar tonsil location in every age range. Two thousand four hundred patients were randomly selected from a database of 62,533 consecutive patients undergoing MRI and were organized into 8 age groups. Magnetic resonance images were directly examined for tonsil location, morphology, and other features. Patients with a history or imaging findings of posterior fossa abnormalities unrelated to Chiari malformation (CM) were excluded from analysis. The caudal extent of the cerebellar tonsils was measured at the midsagittal and lowest parasagittal positions. The mean tonsil height decreased slightly with advancing age into young adulthood and increased with advancing age in the adult age range. An increasing age in the adult age range was associated with a decreased likelihood of a tonsil position 5 mm or more below the foramen magnum (p = 0.0004). In general, the lowest tonsil position in each age group was normally distributed. Patients with pegged morphology were more likely to have a tonsil location at least 5 mm below the foramen magnum (85%), as compared with those having intermediate (38%) or rounded (2%) morphology (p < 0.0001). Female sex was associated with a lower mean tonsil position (p < 0.0001). Patients with a lower tonsil position also tended to have an asymmetrical tonsil position, usually lower on the right (p < 0.0001). Cerebellar tonsil position follows an essentially normal distribution and varies significantly by age. This finding has implications for advancing our understanding of CM.

Impact of tethered cord release on symptoms of Chiari II malformation in children born with a myelomeningocele

PurposeThe role of distal traction in the form of a tethered spinal cord in exacerbating anatomical findings or symptoms of Chiari II malformation (CIIM) has been debated for decades. Despite the association of Chiari II malformation with myelomeningocele, the impact of tethered cord release on CIIM symptoms in patients has not been explored.MethodsA retrospective review of 59 patients born with a myelomeningocele was performed. A total of 92 untethering procedures were performed in which symptoms of CIIM were present in 29 cases. In 57 out of 92 cases, the patients did not have symptoms of CIIM prior to untethering. Six cases were excluded because cervicomedullary decompression was performed prior to untethering. The response of CIIM symptoms, syrinx size, and cerebellar tonsil position were examined before and after spinal cord untethering.ResultsForty-four characteristic signs and symptoms of CIIM were present prior to 29 untetherings. Thirty-three of 44 (75%) symptoms improved following spinal cord untethering, though no symptom resolved completely. Syrinx size and cerebellar tonsil position were unchanged following untethering.ConclusionThe authors conclude that mild to moderate symptoms of CIIM may respond positively to spinal cord untethering, potentially by normalization cerebrospinal fluid flow dynamics. Symptom improvement occurs despite the lack of radiographic evidence of CIIM resolution.

Morphological and Functional Electrophysiological Evidence of Relative Spinal Cord Tethering in Adolescent Idiopathic Scoliosis

Magnetic resonance (MR) imaging and multiplanar reconstruction was used to evaluate the morphology and relative position of the spinal cord in adolescent idiopathic scoliosis (AIS). To determine the longitudinal and cross-sectional morphology of spinal cord in AIS subjects versus normal controls and their correlation with relative position of cerebellar tonsils and somatosensory cortical evoked potentials (SSEP). Our previous studies revealed significantly reduced spinal cord to vertebral column length ratios in AIS patients with severe scoliotic curves suggesting the presence of disproportional growth between the neural and skeletal system. A possible neural origin of etiopathogenesis of AIS is suggested. MR multiplanar reconstruction was performed in 97 adolescent girls (35 moderate, 26 severe AIS with right-sided thoracic/thoracolumbar curve, and 36 age-matched controls). Measurements of the ratio of anteroposterior (AP) and transverse (TS) diameter of the cord, the concave and convex lateral cord space (LCS) were obtained at the apical level in AIS subjects. Same parameters were obtained in normal controls at matched vertebral levels. Correlations were made with cord to vertebral column length ratio, cerebellar tonsil position and SSEP findings. AP/TS cord ratio and LCS ratio were increased in AIS subjects in the presence of reduced spinal cord to vertebral length ratio when compared with normal controls (P < 0.05). The above ratios were exaggerated in AIS subjects with abnormal SSEP findings. The AP/TS cord ratio and LCS ratio were negatively correlated with the cord to vertebral column length ratio (rho = -0.410 and -0.313, P < 0.01) and cerebellar tonsillar level (rho = -0.309 and -0.432, P < 0.01). Our study suggests presence of tethering and increased tension along the longitudinal axis of spinal cord with associated morphologic changes of cross-sectional shape and relative position of the cord.

The role of limited posterior fossa craniectomy in the surgical treatment of Chiari malformation Type I: experience with a pediatric series

Despite progress in the understanding of the causes and pathophysiology of Chiari malformation Type I (CM-I), definitive surgical treatment remains unresolved. Various techniques have been propounded over the years, but there is no general consensus on the most appropriate surgical management for this condition. The authors report their experience with the surgical treatment of 30 pediatric patients with CM-I. The results obtained in 30 patients who underwent surgery for symptomatic CM-I with a purely extradural procedure were retrospectively reviewed. The patient age at operation ranged from 2 months to 16 years (mean 68 months). In 26 patients the CM-I occurred as an isolated disease, whereas in four a recognized bone anomaly involving the cranial base (achondroplasia) was observed. All patients underwent suboccipital craniectomy, which was accompanied by C-1 laminectomy in 22. In all cases a thick fibrous band at the level of foramen magnum was resected; in 11 children serial incisions of the outer layer of the dura mater were performed as well to expand the posterior fossa volume. The follow-up duration varied from a minimum of 12 months to 12.6 years (mean 4.7 years). The most frequent symptoms and signs were head and/or neck pain (56.7%), followed by vertigo (27.7%), upper-and lower-extremity weakness (20.0%), and ataxia (20.0%). Syringomyelia was noted in 12 patients (40.0%) on magnetic resonance (MR) images. Improvement in or resolution of clinical symptoms and signs was observed in all patients. However, only minimal or no modifications could be found in the position of cerebellar tonsils on postoperative MR images in most patients (only occasional improvement in tonsillar herniation), whereas syringomyelic cavitations reduced in size in half of the cases. Nevertheless, in only two patients was a reoperation necessary. In the authors' experience, suboccipital craniectomy and C-I laminectomy (eventually integrated by dural delamination) can represent an effective treatment for symptoms associated with CM-I.