Fossa Volume Research Articles

The posterior cranial fossa: a comparative MRI-based anatomic study of linear dimensions and volumetry in a homogeneous South Indian population.

The posterior fossa contains structures that are vital to life. In this study, we aimed at establishing normal linear dimensions and volume data of the posterior fossa in a homogeneous south Indian population. We also evaluated the influence of large tumors on these parameters. We evaluated the accuracy of different techniques of measuring these dimensions and compared them with literature. Control and tumor MRIs were selected from an imaging database. Linear posterior fossa dimensions as well as volumes were measured using Image J and Fiji. The volume data were compared with similar data from literature. The effect of the presence of a tumor on posterior fossa volume was measured. The posterior fossa volume was higher in men than in women, irrespective of whether the volume was estimated on axial, sagittal or coronal MR images. Despite the wide variation in the techniques used, there was no significant difference between the volumes reported in literature and the volumes calculated in the current series. The presence of large tumors did not affect linear dimensions or posterior fossa volumes. Among the techniques based on linear measurements that were assessed for concordance with manual segmentation, the technique using the formula for volume of an ellipsoid had the best agreement. Posterior fossa volume is higher in men than in women, Posterior fossa dimensions were not affected by the presence of large tumors. Manual segmentation remains the most accurate method to measure posterior fossa volume.

Does a small posterior fossa increase nerve vascular conflict in trigeminal neuralgia?

Magnetic resonance imaging (MRI) can be helpful in visualizing neurovascular conflict (NVC) of the trigeminal nerve in patients with trigeminal neuralgia (TN), but the relationship between these two events is controversial. To investigate whether posterior fossa volume is a predisposing factor for NVC in TN. We conducted a case-control study of clinically diagnosed idiopathic TN of 30 patients aged 30-79 years and 30 age- and sex-matched controls. We compared the volume of the posterior fossa and subarachnoid space using fast-imaging employing steady-state acquisition MRI and the iPlan® programme of BrainLab. The posterior fossa volumes in controls and patients with TN were 168.97 cm(3) and 167.63 cm(3), respectively. A small pontomesencephalic cistern volume was more frequent in TN. However, neither the cisternal nor parenchymal portions of the posterior fossa were different between patients with TN and controls, and no significant volume difference was observed in this study. Although the hypothesis that small posterior fossa volume influences TN was feasible, we did not find any volumetric differences (including the cisternal and parenchymal volumes).However, small pontomesencephalic cistern volumes were more frequent in patients with TN.

Effect of timing of surgical SSP tendon repair on muscle alterations.

To investigate the impacts of delayed repairs of a supraspinatus tendon tear on the supraspinatus muscle, we used an animal model data from two previously published studies in which one supraspinatus (SSP) tendon was detached. In one cohort, the rabbits were killed in groups of 10 at 4, 8, and 12 weeks. In the other cohort, a repair was done at these time points, 12 rabbits each, and the animals killed were 12 weeks later. SSP fossa volume (Muscle belly plus extramuscular fat [e-fat] volume), percentage of intramuscular fat (i-fat), and muscle tissue volume (muscle belly volume minus i-fat), as well as CT determination of e-fat and i-fat of both cohorts, were compared. Fossa volume increased (p < 0.05). Muscle belly and muscle tissue volumes did not increase after repair (p > 0.05), but early repair prevented further volume losses, a fact not seen after 8 and 12 weeks delay of repair. No reversal of e-fat or of i-fat occurred, in fact i-fat almost doubled after 4 weeks delay of repair (p < 0.05). CT studies confirmed the fat results. We conclude that early repair prevented loss of muscle belly and muscle tissue volumes, but that it has no positive influence on fat accumulation.

The Temporal Region in Unilateral Coronal Craniosynostosis

The temporal region is significantly affected by both restricted and compensatory growth in unilateral coronal craniosynostosis. Recurrent deformity in this region after fronto-orbital advancement often requires a revision operation in adolescence. The authors performed a three-dimensional analysis of the temporal region in patients with unilateral coronal craniosynostosis to define the baseline deformity and the immediate and long-term changes after fronto-orbital advancement. A retrospective analysis of patients with nonsyndromic unilateral coronal craniosynostosis who underwent reconstruction with fronto-orbital advancement or revision cranioplasty after fronto-orbital advancement between 2005 and 2010 was performed. Volumetric and craniometric computed tomographic data were obtained from the bilateral temporal regions and analyzed using the appropriate statistical tests. Fifteen patients immediately before and after fronto-orbital advancement and 14 precranioplasty patients were included. In all groups, the supraorbits on the synostotic sides were significantly constricted in the transverse dimension. The temporal fossa volume on the synostotic side was displaced and significantly smaller than the nonsynostotic side in all groups. The temporalis muscle of the synostotic side was smaller but disproportionately large for the temporal fossa. In unilateral coronal craniosynostosis, there is a baseline and persistent deficiency in the transverse dimension of the supraorbit on the synostotic side. The temporalis muscle is smaller on the synostotic side but is disproportionately large for the temporal fossa of the affected side, which is inferolaterally displaced and smaller because of compensatory growth. These subtle abnormalities in the relationships between the bony dimensions and soft tissues appear to contribute to the temporal hollow deformity often observed after fronto-orbital advancement. Therapeutic, III.

The effect of image-guided radiation therapy on rectal and urinary toxicity when radiating the prostatic fossa.

137 Background: The 2013 ASTRO/AUA consensus statement reports that most outcome data for patients with biochemical failure is based on the use of older treatment techniques. Studies reporting outcomes for patients treated with modern techniques are needed. Methods: Patients were treated using the EORTC guidelines for determining the prostate fossa volume and radiation dose was above 64 Gray. 3D conformal planning and 3D treatment techniques including IMRT and VMAT were used. Daily image guidance was introduced in 2008 using cone beam CT scan and KV/KV imaging using surgical clips as fiducial markers. Toxicity and side effects were recorded and compared to patients treated prior to introduction of image guidance. Results: The Table shows toxicity results prior to and after introduction of daily image guidance. χ2 analysis indicates significant differences for GI, GU and overall toxicity between pre-IGRT and post-IGRT patient groups. Conclusions: Our results are consistent with other reports showing that salvage radiation therapy to the prostatic fossa or prostatic fossa and pelvic lymph nodes is well tolerated with few significant acute or late complications. We noted a significant decrease in GI toxicity and in GU toxicity with the introduction of image guidance techniques. [Table: see text]

Assessment of growth dynamics of human cranium middle fossa in foetal period.

Available literature analysis demonstrated smallness of studies of cranial base. The goal of the study was to analyse the medial fossa of the human cranium in the foetal period against other fossae. Survey material consisted of 110 human foetuses at a morphological age of 16-28 weeks of foetal life, CRL 98-220 mm. Anthropological, preparation method, reverse method and statistical analysis were utilized. The survey incorporated the following computer programmes: Renishaw, TraceSurf, AutoCAD, CATIA. The reverse method seems especially interesting (impression with polysiloxane (silicone elastomer of high adhesive power used in dentistry) with 18 D 4823 activator. Elicited impression accurately reflected complex shape of cranium base. On assessing the relative rate of cranium medial fossa, the rate was found to be stable (linear model) for the whole of the analysed period and is 0.19%/week, which stands for the gradual and steady growth of the middle fossa in relation to the whole of the cranium base. At the same time, from the 16th till 28th week of foetal life, relative volume of the cranium middle fossa increases more intensively than cranium anterior fossa, whereas the cranium middle fossa volume as compared with the cranium posterior fossa is definitely slower. In the analysed period, the growth rate of the cranium base middle fossa was bigger in the 4th and 5th weeks than in the 6th and 7th weeks of foetal life. The investigations revealed cranium base asymmetry of the left side. Furthermore, the anterior fossae volume on the left side is significantly bigger than the one of the fossae on the right side. Volume growth rate is more intensive in the 4th and 5th than in the 6th and 7th weeks of foetal life. In the examined period, the relative growth rate of cranium base middle fossa is 0.19%/week and it is stable - linear model. The study revealed correlations in the form of mathematical models, which enabled foetuses age assessment.

Stereotactic radiosurgery for arteriovenous malformations of the cerebellum

Arteriovenous malformations (AVMs) of the posterior fossa have an aggressive natural history and propensity for hemorrhage. Although the cerebellum accounts for the majority of the posterior fossa volume, there is a paucity of stereotactic radiosurgery (SRS) outcome data for AVMs of this region. The authors sought to evaluate the long-term outcomes and risks of cerebellar AVM radiosurgery. This single-institution retrospective analysis reviewed the authors' experience with Gamma Knife surgery during the period 1987-2007. During this time 64 patients (median age 47 years, range 8-75 years) underwent SRS for a cerebellar AVM. Forty-seven patients (73%) presented with an intracranial hemorrhage. The median target volume was 3.85 cm(3) (range 0.2-12.5 cm(3)), and the median marginal dose was 21 Gy (range 15-25 Gy). Arteriovenous malformation obliteration was confirmed by MRI or angiography in 40 patients at a median follow-up of 73 months (range 4-255 months). The actuarial rates of total obliteration were 53% at 3 years, 69% at 4 years, and 76% at 5 and 10 years. Elevated obliteration rates were statistically higher in patients who underwent AVM SRS without prior embolization (p = 0.005). A smaller AVM volume was also associated with a higher rate of obliteration (p = 0.03). Four patients (6%) sustained a hemorrhage during the latency period and 3 died. The cumulative rates of AVM hemorrhage after SRS were 6% at 1, 5, and 10 years. This correlated with an overall annual hemorrhage rate of 2.0% during the latency interval. One patient experienced a hemorrhage 9 years after confirmed MRI and angiographic obliteration. A permanent neurological deficit due to adverse radiation effects developed in 1 patient (1.6%) and temporary complications were seen in 2 additional patients (3.1%). Stereotactic radiosurgery proved to be most effective for patients with smaller and previously nonembolized cerebellar malformations. Hemorrhage during the latency period occurred at a rate of 2.0% per year until obliteration occurred.

Evolutionary hypothesis for Chiari type I malformation

Chiari I malformation (CM-I) is classically defined as a cerebellar tonsillar herniation (⩾5mm) through the foramen magnum. A decreased posterior fossa volume, mainly due to basioccipital hypoplasia and sometimes platybasia, leads to posterior fossa overcrowding and consequently cerebellar herniation. Regardless of radiological findings, embryological genetic hypothesis or any other postulations, the real cause behind this malformation is yet not well-elucidated and remains largely unknown. The aim of this paper is to approach CM-I under a broader and new perspective, conjoining anthropology, genetics and neurosurgery, with special focus on the substantial changes that have occurred in the posterior cranial base through human evolution. Important evolutionary allometric changes occurred during brain expansion and genetics studies of human evolution demonstrated an unexpected high rate of gene flow interchange and possibly interbreeding during this process. Based upon this review we hypothesize that CM-I may be the result of an evolutionary anthropological imprint, caused by evolving species populations that eventually met each other and mingled in the last 1.7million years.

“Triple R” tonsillar technique for the management of adult Chiari I malformation: surgical note

Chiari type I malformation is a congenital disorder that is characterized by the caudal extension of the cerebellar tonsils through the foramen magnum into the cervical canal and by a reduced posterior fossa volume. We report our surgical technique of reposition, reduction, or resection of the cerebellar tonsils for the management of Chiari I malformation. The procedure was performed in 22 adult patients, in three different centers, with a mean age of 37 years. Clinical complaints included headaches, nuchalgia, vertigo, and upper-limb weakness or numbness. Seven patients had cervical syringomyelia. Symptoms developed within a mean time of 36 months (range, 12-70 months). The cerebellar tonsils were exposed through a dura mater-arachnoid incision at the atlanto-occipital space after a 0.5-cm rimming craniectomy of the occipital bone in all patients. In seven patients the tonsils were resected, in other seven were reduced by subpial coagulation and aspiration, and in the remaining eight patients the tonsils were repositioned after coagulating their surfaces. Three patients had also a posterior fossa arachnoid cyst that was fenestrated in two of them. All patients improved postoperatively. Syringomyelia was reduced in five of seven patients. The mean length of the follow-up period was 12 months. Selective reposition, reduction, or resection of herniated cerebellar tonsils may improve symptoms in adult patients with Chiari I malformation.

Trigeminal Nerve Morphology in Alligator mississippiensis and Its Significance for Crocodyliform Facial Sensation and Evolution

Modern crocodylians possess a derived sense of face touch, in which numerous trigeminal nerve-innervated dome pressure receptors speckle the face and mandible and sense mechanical stimuli. However, the morphological features of this system are not well known, and it remains unclear how the trigeminal system changes during ontogeny and how it scales with other cranial structures. Finally, when this system evolved within crocodyliforms remains a mystery. Thus, new morphological insights into the trigeminal system of extant crocodylians may offer new paleontological tools to investigate this evolutionary transformation. A cross-sectional study integrating histological, morphometric, and 3D imaging analyses was conducted to identify patterns in cranial nervous and bony structures of Alligator mississippiensis. Nine individuals from a broad size range were CT-scanned followed by histomorphometric sampling of mandibular and maxillary nerve divisions of the trigeminal nerve. Endocast volume, trigeminal fossa volume, and maxillomandibular foramen size were compared with axon counts from proximal and distal regions of the trigeminal nerves to identify scaling properties of the structures. The trigeminal fossa has a significant positive correlation with skull length and endocast volume. We also found that axon density is greater in smaller alligators and total axon count has a significant negative correlation with skull size. Six additional extant and fossil crocodyliforms were included in a supplementary scaling analysis, which found that size was not an accurate predictor of trigeminal anatomy. This suggests that phylogeny or somatosensory adaptations may be responsible for the variation in trigeminal ganglion and nerve size in crocodyliforms.

Spinal level of myelomeningocele lesion as a contributing factor in posterior fossa volume, intracranial cerebellar volume, and cerebellar ectopia

McLone and Knepper's unified theory of Chiari malformation Type II (CM-II) describes how the loss of CSF via the open posterior neuropore fails to create adequate distending pressure for the developing rhomboencephalic vesicle. The authors of the present article describe the relationship between the posterior fossa volume and intracranial cerebellar volume as being related to the distance from the obex of the fourth ventricle to the myelomeningocele lesion using a common mathematical model, the Hagen-Poiseuille law. All newborns who required closure of a myelomeningocele at the authors' institution between 2008 and 2011 and who were between 4 weeks premature and 2 months, corrected gestational age, at the time of MRI were included in this study. Volumes and measurements were obtained from axial and sagittal T2-weighted MR images of the brain and spine. A total of 56 newborn infants met the inclusion criteria. There was a direct linear relationship between both posterior fossa volume and cerebellar volume and the spinal level of the myelomeningocele lesion (p = 0.0012 and p = 0.0041, respectively). There was a negative linear relationship between the cerebellar descent, the spinal level of the lesion, and posterior fossa volume and cerebellar volume. These relationships strengthen in patients with no syringomyelia and are not significant in those groups with syringomyelia. The results of a 1-way ANOVA for the 3 groups did not reach significance. Using a linear equation derived from the Hagen-Poiseuille law that describes pressure in the fourth ventricle as being directly related to the length of the central canal from the obex to the myelomeningocele lesion, the authors were able to explain the directly observed linear relation between posterior fossa volume, intracranial cerebellar volume, and cerebellar descent to the level of the spinal lesion. As this model assumes a uniform radius of the central canal they were able to validate this model when they observed a strengthening in relationships in the no syringomyelia group and statistically insignificant correlations in the groups with syringomyelia. They therefore propose that the spinal level of the lesion is one of the major determinants of posterior fossa volume, intracranial cerebellar volume, and cerebellar ectopia.

Morphometric analysis of posterior fossa and foramen magnum

Introduction:Configuration and size of the foramen magnum and posterior fossa plays an important role in the pathophysiology of the posterior fossa and craniovertebral junction disorders. This study is aimed to find out various dimensions of the foramen magnum and posterior fossa.Materials and Methods:This is a prospective study of 100 consecutive normal computerized tomography (CT) scans of posterior fossa and 100 dry adult skulls without any bony abnormality. The posterior fossa volume was calculated by abc/2 in method 1 and by advanced work station of CT scan in method 2. Various dimensions of posterior fossa and foramen magnum were also studied.Results:Age ranged from 16 to 89 years with a mean of 51.3 years. Mean height of posterior fossa were 3.01 cm (±0.22) and 3.52 (±0.43) cm in dry skull and CT scan group, respectively (P < 0.0001). Mean volume of posterior fossa were 157.88 (±27.94) cm3 and 159.58 (±25.73) cm3 by method 1 and method 2, respectively (P > 0.05). All the dimensions of posterior fossa and foramen magnum were larger in male as compared to female. Mean anteroposterior (AP), transverse diameter and surface area of the foramen magnum were 3.31 (±0.35) cm, 2.76 (±0.31) cm, and 729.15 (±124.87) mm2, respectively, in CT scan group as compared to 3.41 (±0.29) cm, 2.75 (±0.25) cm, and 747.67 (±108.60) mm2, respectively, in dry skull group.Conclusion:Normal values of posterior fossa and foramen magnum could serve as a future reference. Dry skull dimensions could be different from CT scan measurement. More studies are needed as there could be variations in dimensions in different regions in India

Treatment of Chiari malformation combined with basilar invagination by staged anterior and posterior decompression

Objective There is usually anterior compression of the brain stem in Chiari malformation patients combined with basilar invagination.After anterior decompression,many patients will present elevation of the cerebellar tonsil and resolution of syringomyelia.However,still in some patients,the Chiari malformation and syringomyelia remain unchanged after anterior decompression.This article is to discuss a staged anterior and posterior decompression strategy for the treatment of these patients.Methods 9 cases of Chiari malformation combined with basilar invagination were operated by transoral transpharyngeal odontoidectomy first,observed for 1 -2 months,the Chiari malformation and syringomyelia did not relieve,then posterior foramen magnum decompression,tonsillectomy and expansion of posterior fossa dura combined with occipito - cervical fusion or C1-2 fusion were performed.The patients were followed up for 24 - 60 months ( mean 32 months).Results There was no mortality or severe complication.The clinical symptoms were improved in all patients.The Chiari malformation and syringomyelia were relieved in 8 patients,while unchange in 1 case.Conclusions For Chiari malformation patients combine with basilar invagination,anterior decompression with odontoidectomy should be performed first. In many patients,increase ofposterior fossa volume,improved CSF dynamic may be achieved,posterior fusion will be enough.While in some other patients,only symptoms of basilar invagination may be improved after anterior decompression.So posterior decompression is still important. Key words: Platybasia; Arnold - Chiari malformation; Cranio - vertebral junction malformation; Odontoidectomy ; Occipito - cervical fusion

Analysis of the Volumes of the Posterior Cranial Fossa, Cerebellum, and Herniated Tonsils Using the Stereological Methods in Patients with Chiari Type I Malformation

Objective. The aim of this study was to determine the posterior cranial fossa volume, cerebellar volume, and herniated tonsillar volume in patients with chiari type I malformation and control subjects using stereological methods. Material and Methods. These volumes were estimated retrospectively using the Cavalieri principle as a point-counting technique. We used magnetic resonance images taken from 25 control subjects and 30 patients with chiari type I malformation. Results. The posterior cranial fossa volume in patients with chiari type I malformation was significantly smaller than the volume in the control subjects (P < 0.05). In the chiari type I malformation group, the cerebellar volume was smaller than the control group, but this difference was not statistically significant (P > 0.05). In the chiari type I malformation group, the ratio of cerebellar volume to posterior cranial fossa volume was higher than in the control group. We also found a positive correlation between the posterior cranial fossa volume and cerebellar volume for each of the groups (r = 0.865, P < 0.001). The mean (±SD) herniated tonsillar volume and length were 0.89 ± 0.50 cm3 and 9.63 ± 3.37 mm in the chiari type I malformation group, respectively. Conclusion. This study has shown that posterior cranial fossa and cerebellum volumes can be measured by stereological methods, and the ratio of these measurements can contribute to the evaluation of chiari type I malformation cases.

Changes over time in craniocerebral morphology and syringomyelia in cavalier King Charles spaniels with Chiari-like malformation

BackgroundChiari-like malformation (CM) and syringomyelia is a neurological disease complex with high prevalence in cavalier King Charles spaniels (CKCS). The natural progression of this disease with time has not been described. The objectives of this study were to i) determine if syringomyelia progresses with time ii) determine if features of craniocrebral morphology previously associated with CM are progressive (including caudal cranial fossa volume, caudal cranial fossa parenchymal volume, ventricular dimensions, height of the foramen magnum and degree of cerebellar herniation). A retrospective morphometric analysis was undertaken in 12 CKCS with CM for which repeat magnetic resonance images were available without surgical intervention.ResultsThe maximal syrinx width, height of the foramen magnum, length of cerebellar herniation and caudal cranial fossa volume increased over time. Ventricular and caudal fossa parenchymal volumes were not significantly different between scans.ConclusionsThe results of this study suggest that syringomyelia progresses with time. Increased caudal cranial fossa volume may be associated with active resorption of the supraoccipital bone, which has previously been found in histology specimens from adult CKCS. We hypothesise that active resorption of the supraoccipital bone occurs due to pressure from the cerebellum. These findings have important implications for our understanding of the pathogenesis and variable natural clinical progression of CM and syringomyelia in CKCS.

Craniovertebral junction abnormalities with hindbrain herniation and syringomyelia: regression of syringomyelia after removal of ventral craniovertebral junction compression

Hindbrain herniation syndrome, or Chiari malformation Type I (CM-I), occurs frequently with craniovertebral junction (CVJ) abnormalities when there is reduction in the posterior fossa volume. Syringomyelia is often present. Posterior fossa dorsal decompression (PFDD) is typically performed but has adverse results when ventral bone abnormality exists. This paper presents the results of a prospective study on CVJ abnormalities in patients with CM-I and syringomyelia. Between 1984 and 2008 (the MR imaging era), 298 patients with CVJ abnormalities and CM-I underwent ventral cervicomedullary decompression. Eighty-four patients had associated syringomyelia (15 with secondary invagination and 69 with primary basilar invagination, os odontoideum, or malunion of fractures). Of these 84 patients with CVJ abnormalities, CM-I, and syringomyelia, 46 had previously undergone PFDD, and 28 had previously undergone PFDD combined with fusion procedures or shunt placements. Of the 84 patients, a cervicothoracic syrinx was observed in 57, thoracic syrinx in 14, and holocord syrinx in 13. Studies included CT, MR imaging, and cine flow studies. All 298 patients who underwent ventral CVJ decompression had irreducible or partially reducible pathology. All 84 with syringomyelia showed brainstem dysfunction, lower cranial nerve symptoms, or myelopathy. Brainstem signs improved in 66 of the 84 patients, myelopathy improved in 58, and syringomyelia regressed in 64. Neurological improvement and syringomyelia resolution can occur using only ventral cervicomedullary junction decompression in patients with basilar invagination and basilar impression. This is likely due to the relief of neural encroachment and reestablishment of CSF pathways.

Editorial: Chiari malformation Type I

In their paper, Noudel et al. carefully analyzed the presentation, change in posterior fossa volume (PFV), and outcome of a series of 11 adult patients undergoing posterior fossa (PF) decompression for Chiari malformation Type I (CM-I).1 They performed an occipital craniectomy and C-1 laminectomy with dural opening and expansion but with meticulous preservation of the arachnoid layer. Their craniectomy was approximately 3 × 3 cm. The authors state that this may be less than optimal in some individuals. They conclude that the clinical response to surgery was significantly influenced by the extent of the PFV expansion and that an ideal bony expansion can be predicted based on preoperative MR imaging findings. Of the many issues surrounding CM-I surgery, the extent of bony decompression is 1 of the 3 most pertinent issues discussed today. The other 2 issues regard which clinical symptoms will respond to surgery and which anatomical layers should be included in the decompression. The authors propose and validate a technique to measure PFV and then use the technique to assess a response to surgery. Limitations of the study include the small number of patients analyzed (11), the varying types of their presentation and preoperative imaging findings, and the relatively short duration of follow-up of a chronic disease. The absolute measurements should not be applied to pediatric patients, and the technique of dural opening is especially challenging with the large venous sinuses seen over the PF in small infants and children. A small percentage (5%– 10%) of patients with CM-I will have a medullary veil or some other type of physical or inflammatory obstruction at the outlet of the fourth ventricle, limiting rapid CSF equilibration without intraarachnoidal exploration. By not opening the arachnoid, the authors forfeit the possible clinical improvement in this minority of patients for fear of subarachnoid contamination with blood and the other potential complications associated with intraarachnoidal inspection. The surgical approach emphasizes the maintenance of the arachnoid to protect the subarachnoid space and the need for a meticulous closure. Soiling of the subarachnoid space with blood or other inflammatory material can be counterproductive to the goal of maintaining free and easy CSF egress from the fourth ventricular outlet. The authors conclude that a larger bony opening yields a more favorable clinical outcome. The reader is told that no patient suffered from cerebellar “slump” as a consequence of too aggressive of a bony decompression but that this possibility certainly exists, especially when the decompression exceeds 4 × 4 cm. Adding objective measurement of the extent of the bony removal in a CM-I decompression adds significantly to the surgical refinement of this relatively common procedure.

Endoscopic Third Ventriculostomy for the Management of Chiari I and Related Hydrocephalus: Outcome and Pathogenetic Implications

Hydrocephalus affects 7% to 10% of patients with Chiari I malformation (CIM). It can be successfully treated by endoscopic third ventriculostomy (ETV), possibly improving related CIM and syringomyelia. To confirm the effectiveness of ETV in the management of Chiari-related hydrocephalus and symptoms and to estimate the posterior cranial fossa volume (PCFV) to find the possible reasons for the success or failure of ETV. Fifteen patients (11 children and 4 adults) underwent ETV for hydrocephalus associated with CIM (syringomyelia was present in 6 patients). Preoperative PCFV, posterior fossa brain volume (PFBV), and PFBV/PCFV ratio were calculated in the last 12 patients in the series by a magnetic resonance imaging-based computerized method. All patients had symptomatic hydrocephalus (mean third ventricle diameter, 14.1 mm). Mean tonsillar ectopia was 12.7 mm. Postoperatively, hydrocephalus symptoms improved in all cases (mean third ventricle diameter, 8.3 mm); signs and symptoms of CIM and syringomyelia resolved or improved in all patients, although the malformation remained radiologically stable in half of the patients (postoperative mean tonsillar ectopia, 8.8 mm). There were no remarkable differences between cases and controls with regard to PCFV and PFBV. The PFBV/PCFV ratio was comparable in pediatric cases and controls but not among adult patients, suggesting a PCF overcrowding in the controls. ETV is an effective treatment for hydrocephalus associated with CIM. It is successful in improving CIM and syringomyelia in patients with no overcrowding (mainly in children) or with reversible overcrowding of the PCF (mainly in adults).

Posterior fossa volume increase after surgery for Chiari malformation Type I: a quantitative assessment using magnetic resonance imaging and correlations with the treatment response

The aim of this paper was to measure the posterior fossa (PF) volume increase resulting from a given-sized occipital craniectomy in Chiari malformation Type I surgery and to analyze its correlations with the PF size and the treatment response, with the perspective of tailoring the amount of bone removal to the patient-specific PF dimensions. Between January 2005 and June 2006, 11 adult patients with symptomatic Chiari malformation Type I underwent a standardized PF decompression. A prospective evaluation with clinical examination, functional grading, and MR imaging measurement protocols was performed pre- and postoperatively. A method is reported for the measurement of PF volume (PFV) after surgery. The degree of PFV increase was compared with the preoperative size of the PF and with the clinical outcome. All 11 patients improved postoperatively, with complete and partial recovery in 4 and 7 patients, respectively. No postoperative complication occurred after a mean follow-up period of 45 months. The mean relative increase in PFV accounted for 10% (range 1.5%-19.7%) of the initial PFV; the increase was greater in cases in which the PF was small (r = -0.52, p = 0.09) and the basiocciput was short (r = -0.37, p = 0.2). A statistically significant positive correlation was found between the degree of PFV increase and the treatment response (p = 0.014); complete recovery was observed with a PFV increase of 15% and partial recovery with an increase of 7%. The treatment response is significantly influenced by the degree of PFV increase, which is dependent on the size of the PF and the extent of the craniectomy, suggesting that the optimal patient-specific PFV increase could be predicted on the basis of preoperative MR imaging and enhancing the perspective that the craniectomy size could be tailored to the individual PFV.

Is Chiari I Malformation Associated With Fibromyalgia?

The symptoms of Chiari I Malformation (CIM) and fibromyalgia (FM) overlap. Some FM patients have been surgically treated for presumed CIM-type pathology. To determine whether CIM is more common among FM patients than pain- and fatigue-free controls. One hundred seventy-six participants with FM and 67 pain- and fatigue-free control subjects underwent magnetic resonance imaging of the brain and upper cervical spine. Posterior fossa cerebrospinal fluid flow was assessed with cardiac gated cine phase-contrast imaging at the craniocervical region. CIM was defined as inferior extension of cerebellar tonsils ≥ 5 mm below the basion-opisthion line of the foramen magnum or tonsillar position 3 to 5 mm below the basion-opisthion line plus abnormalities of CSF flow, posterior fossa volume, or hindbrain or cervical spinal cord movement. Visual analog scales, questionnaires, and interviews were used to collect data on sleep quality, fatigue, pain, and headache. We used regression techniques to examine the association of outcome measures with disease status and the Fisher exact test to compare the CIM prevalence in the 2 groups. The FM group was older (mean age, 50 vs 40 years) and more likely to be white (89% vs 73%) and female (93% vs 54%; P < .01). Mean tonsillar position and the prevalence of CIM (2.8% vs 4.5%; P = .69) were similar in the FM and control groups. FM patients experienced more headaches, pain, fatigue, and sleep disturbances than control subjects (P < .01). Most patients with FM do not have CIM pathology. Future studies should focus on dynamic neuroimaging of craniocervical neuroanatomy in patients with FM.