Acquired Chiari malformation Type I associated with a supratentorial arteriovenous malformation. Case report and review of the literature

Geometric morphometric analysis of the brainstem and cerebellum in Chiari I malformation

Background

Chiari I malformation (CMI) is characterized by inferior descent of the cerebellar tonsils through the foramen magnum and is associated with headache and neck pain. Many morphometric research efforts have aimed to describe CMI anatomy in the midsagittal plane using classical measurement techniques such as linear dimensions and angles. These methods are less frequently applied to parasagittal features and may fall short in quantifying more intricate anatomy with fewer distinct homologous landmarks.

Methods

Landmark-based geometric morphometric techniques were used to asses CMI morphology in five anatomical planes of interest.

Results

Significant shape differences between CMI and age/sex-matched controls were found in the midsagittal (Pseudo-F = 5.4841, p = 0.001) and axial planes through the rostral medulla (Pseudo-F = 7.6319, p = 0.001). In addition to tonsillar descent, CMI principal component 1 (PC1) scores in the midsagittal protocol were associated with marked anterior concavity of the brainstem and generalized verticality of the cerebellum with anterior rotation of its anterior lobe. In the axial medulla/cerebellum protocol, CMI PC1 scores were associated with greater anterior-posterior (A-P) dimension with loss of medial-lateral (M-L) dimension.

Discussion

These results suggest that CMI is associated with greater curvature of the brainstem and spinal cord, which may perturb normal neural activities and disrupt cerebrospinal fluid movements. Previous reports on the A-P diameter of the posterior fossa in CMI have conflicted; our findings of greater A-P cerebellar dimensionality with concomitant loss of width alludes to the possibility that more caudal aspects of the posterior cranial fossa are more bowl-like (homogenous in axial dimensions) and less trough-like or elongated in the M-L direction.

Unveiling the domino effect: a nine-year follow-up on pentalogy of central nervous system induced by a large unruptured cerebral arteriovenous malformation: a case report and literature review

Background

The disruption of intracranial fluid dynamics due to large unruptured cerebral arteriovenous malformation (AVM) commonly triggers a domino effect within the central nervous system. This phenomenon is frequently overlooked in prior clinic and may lead to catastrophic misdiagnoses. Our team has documented the world's first case of so-called AVM Pentalogy (AVMP) induced by a AVM.

Clinical presentation and result

A 30-year-old female was first seen 9 years ago with an occasional fainting, at which time a huge unruptured AVM was discovered. Subsequently, due to progressive symptoms, she sought consultations from several prestigious neurosurgical departments in China, where all consulting neurosurgeons opted for conservation treatment due to perceived surgical risks. During the follow-up period, the patient gradually presented with hydrocephalus, empty sella, secondary Chiari malformation, syringomyelia, and scoliosis (we called as AVMP). When treated in our department, she already displayed numerous symptoms, including severe intracranial hypertension. Our team deduced that the hydrocephalus was the primary driver of her AVMP symptoms, representing the most favorable risk profile for intervention. As expected, a ventriculoperitoneal shunt successfully mitigated all symptoms of AVMP at 21-months post-surgical review.

Conclusion

During the monitoring of unruptured AVM, it is crucial to remain vigilant for the development or progression of AVMP. When any component of AVMP is identified, thorough etiological studies and analysis of cascade reactions are imperative to avert misdiagnosis. When direct AVM intervention is not viable, strategically addressing hydrocephalus as part of the AVMP may serve as the critical therapeutic focus.

Acute Foramen Magnum Syndrome Following Single Diagnostic Lumbar Puncture: Consequence of a Small Posterior Fossa?

BACKGROUND

Type I Chiari malformation (CMI) is a rare complication of lumbar cerebrospinal fluid (CSF) drainage that is usually reported after lumbar drain or lumboperitoneal shunt placement. It usually remains asymptomatic; however, even if it becomes symptomatic, symptoms are usually mild. There are only a few reports of acute foramen magnum syndrome following continuous lumbar CSF drainage, and acute foramen magnum syndrome after a single diagnostic lumbar puncture (LP) has not been previously reported. We encountered this catastrophic complication in one of our patient.

CASE DESCRIPTION

A 30-year-old woman with a large supratentorial meningioma and associated asymptomatic CMI presented with holocranial headache. She underwent successful and uneventful excision of the tumor. However, she developed quadriplegia and respiratory arrest 48 hours following a diagnostic LP performed on postoperative day 9. She underwent urgent posterior fossa decompression after magnetic resonance imaging showed increased tonsillar impaction and swelling along with cervicomedullary compression. Postoperatively, she steadily improved and regained normal power after 3 months. Retrospective quantitative analysis of magnetic resonance imaging (MRI) revealed a small posterior fossa.

CONCLUSIONS

The association of intracranial tumors and lumbar CSF drainage with CMI is uncommon. The documentation of a small posterior fossa signifies the importance of both developmental (small posterior fossa) and acquired (intracranial tumor/lumbar CSF drainage) factors in pathogenesis of CMI. Although the extreme rarity of acute deterioration following a single LP does not warrant LP to be contraindicated in such patients, documentation of resolution of CMI with postoperative MRI before performing lumbar CSF drainage (whether therapeutic or diagnostic), might be helpful in avoiding this rare complication.

Evolution of tonsillar ectopia associated with frontal encephalocoele

INTRODUCTION

Chiari I malformation has been traditionally considered a congenital malformation. However, there is growing clinical evidence suggesting that it is an acquired phenomenon as also exemplified by this case.

CASE

Fetal magnetic resonance imaging (MRI) at 28th week gestation revealed a frontonasal encephalocoele with no hindbrain abnormalities. Post-natal MRI of brain and cervical spine of the 7-week-old infant showed the presence of tonsillar ectopia in the absence of hydrocephalus. The normally developed cerebellar tonsil has herniated through the foramen magnum during the third trimester and neonatal period.

DISCUSSION

We hypothesise that the presence of the encephalocoele resulted in dampening expansile forces, produced by the growing brain as well as the cerebrospinal fluid pulsation required to stimulate of the skull growth. As a result, cranial growth is diminished producing a small posterior fossa. The subsequent growth spurt of the cerebellum at the end of the third trimester and during the neonatal period has resulted in cerebellar tonsillar ectopia consequent upon the state of cephalocranial disproportion.

Acute symptomatic cerebellar tonsillar herniation following intraoperative lumbar drainage

Complications of tonsillar herniation associated with lumbar drainage have been reported in the literature. However, acutely symptomatic tonsillar herniation after intraoperative lumbar drainage is rare. The following case illustrates the risk associated with cerebrospinal fluid (CSF) drainage in the setting of tonsillar herniation. The use of lumbar drainage during cranial surgery is a common practice for reducing intracranial pressure and enhancing exposure, but is not without complications. In addition to the complications of the insertion procedure itself, the change in pressure gradient between the intracranial and the suboccipital compartments is of key importance.

The authors present the case of a patient who underwent a subtemporal craniotomy for resection of mesial temporal cavernous malformation with intraoperative lumbar drainage. The patient had a preexisting, asymptomatic 4-mm Chiari malformation and progressive neurological deficits resulting from further cerebellar tonsillar herniation in the early postoperative period developed, which required a lumbar blood patch, decompressive suboccipital craniectomy, and C-1 laminectomy with duroplasty. After placement of the lumbar drain and subsequent CSF drainage, the change in CSF pressure gradient above and below the foramen magnum probably led to the herniation. Unfortunately, the patient has lasting neuropathic pain and cervical cord signal changes on MR images.

Hydrovenous Disorder in Vein of Galen Aneurysmal Dilatation: Special Focus on Tonsilar Prolapse

We analyzed five cases of vein of Galen aneurysmal dilatation (VGAD) and 12 cases of vein of Galen aneurysmal malformation (VGAM) using sagittal T1-weighted images. Tonsilar prolapse (TP) was confirmed in three cases, which were all VGAD. Two of these cases were treated by endovascular procedures. In one of these two cases, elevation of TP was observed after intervention. There were no signs of TP in the control group of 12 VGAMs. Venous hypertension interferes with cerebrospinal fluid (CSF) resorption resulting in increased brain fluid. TP frequently develops in high flow AVFs and is reversible if therapeutic intervention is performed by an experienced clinical team when appropriately indicated. We consider that TP in VGAD is mainly the result of cerebellar swelling due to chronic venous hypertension.