Neurosurgery Blog

Neurosurgery 67:824-836, 2010 DOI: 10.1227/01.NEU.0000377852.75544.E4

Surgical treatment of arachnoid cysts remains under debate. Although many authors favor endoscopic techniques, others attribute a higher recurrence rate to the endoscope.

OBJECTIVE: The authors report their experience with endoscopic procedures for arachnoid cyst.

METHODS: All pure endoscopic procedures for arachnoid cysts performed by the authors were analyzed. Particular reference was given to surgical complications and patient outcome in relation to cyst location and endoscopic technique.

RESULTS: Sixty-six endoscopic procedures were performed in 61 patients (mean age, 28 years; range, 23 days to 74 years; 35 males, 26 females). The main presenting symptoms were cephalgia (61%), hemisymptoms (18%), and macrocephalus (18%). Cyst location was temporobasal (34%), suprasellar (21%), at the cisterna quadrigemina (18%), paraxial supratentorial (16%), and various (10%). Thirty cystocisternostomies, 14 ventriculocystostomies, 12 cystoventriculostomies, and 10 ventriculocystocisternostomies were performed. The overall clinical success rate was 90%. The endoscopic technique was abandoned in 4 cases (7%). Postoperative complications were found in 16%; there was only one permanent deficit (2%). Five recurrences (8%) occurred up to 7 years after the first procedure. Of the various locations, the temporobasal cysts were the most difficult to treat with lowest clinical success (81%), highest recurrence (19%), and highest complication rate (24%). Of the various endoscopic techniques, ventriculocystostomy and ventriculocystocisternostomy reached the highest success rates with 100%.

CONCLUSIONS: Endoscopic techniques provide very good results in arachnoid cyst treatment. The most frequent cyst location is the most difficult to treat. A long-term follow-up is recommended since recurrences can occur many years after the procedure

Acta Neurochir (2010) 152:1117–1127.DOI 10.1007/s00701-010-0636-3

The pathogenesis of Chiari malformations is incompletely understood. We tested the hypothesis that different etiologies have different mechanisms of cerebellar tonsil herniation (CTH), as revealed by posterior cranial fossa (PCF) morphology.

Methods In 741 patients with Chiari malformation type I (CM-I) and 11 patients with Chiari malformation type II (CM-II), the size of the occipital enchondrium and volume of the PCF (PCFV) were measured on reconstructed 2D-CT and MR images of the skull. Measurements were compared with those in 80 age- and sex-matched healthy control individuals, and the results were correlated with clinical findings.

Results Significant reductions of PCF size and volume were present in 388 patients with classical CM-I, 11 patients with CM-II, and five patients with CM-I and craniosynostosis. Occipital bone size and PCFV were normal in 225 patients with CM-I and occipitoatlantoaxial joint instability, 55 patients with CM-I and tethered cord syndrome (TCS), 30 patients with CM-I and intracranial mass lesions, and 28 patients with CM-I and lumboperitoneal shunts. Ten patients had miscellaneous etiologies. The size and area of the foramen magnum were significantly smaller in patients with classical CM-I and CM-I occurring with craniosynostosis and significantly larger in patients with CM-II and CM-I occurring with TCS.

Conclusions Important clues concerning the pathogenesis of CTH were provided by morphometric measurements of the PCF. When these assessments were correlated with etiological factors, the following causal mechanisms were suggested: (1) cranial constriction; (2) cranial settling; (3) spinal cord tethering; (4) intracranial hypertension; and (5) intraspinal hypotension

AJNR Am J Neuroradiol 31:997–1002.DOI 10.3174/ajnr.A1995

CSF flow has been shown to exhibit complex patterns in MR images in both healthy subjects and in patients with Chiari I. Abnormal CSF flow oscillations, according to prevailing opinion, cause syringomyelia and other clinical manifestations that affect some patients with the Chiari I malformation.

For this article, we reviewed the literature on PC MR of CSF flow, collected the published CFD studies relevant to CSF flow, and performed flow simulations. PC MR creates cine and still images of CSF flow and measurements of flow velocities. CFD, a technique used to compute flow and pressure in liquid systems, simulates the CSF flow patterns that occur in a specific geometry or anatomy of the SAS and a specific volume of flow.

Published PC MR studies show greater peak CSF velocities and more complex flow patterns in patients with Chiari I than in healthy subjects, with synchronous bidirectional flow one of the characteristic markers of pathologic flow. In mathematic models of the SAS created from high-resolution MR images, CFD displays complex CSF flow patterns similar to those shown in PC MR in patients. CFD shows that the pressure and flow patterns vary from level to level in the upper spinal canal and differ between patients with Chiari and healthy volunteers. In models in which elasticity and motion are incorporated, CFD displays CSF pressure waves in the SAS.

PC MR and CFD studies to date demonstrate significant alterations of CSF flow and pressure patterns in patients with Chiari I. CSF flow has nonlaminar complex spatial and temporal variations and associated pressure waves and pressure gradients. Additional simulations of CSF flow supplemented by PC MR will lead to better measures for distinguishing pathologic flow abnormalities that cause syringomyelia, headaches, and other clinical manifestations in Chiari I malformations.

CFD  computational fluid dynamics; PC MR  phase-contrast cardiac-gated MR studies; SAS  subarachnoid space

Neurosurg Focus 29 (1):E9, 2010. (10.3171/2010.3.FOCUS1085)

The definition of tethered cord syndrome (TCS) relies mainly on radiological criteria and clinical picture. The presence of a thickened filum terminale and a low-lying conus medullaris in symptomatic patients is indicative of TCS. The radiological definition of TCS does not take into account cases that involve a normal-lying conus medullaris exhibiting symptoms of the disease.

Methods. The authors performed a MEDLINE search using the terms “tethered cord” and “pathophysiology.” The search returned a total of 134 studies. The studies were further filtered to identify mostly basic research studies in animal models or studies related to the biomechanics of the filum terminale and spinal cord.

Results. Spinal cord traction and the loss of filum terminale elasticity are the triggers that start a cascade of events occurring at the metabolic and vascular levels leading to symptoms of the disease. Traction on the caudal cord results in decreased blood flow causing metabolic derangements that culminate in motor, sensory, and urinary neurological deficits. The untethering operation restores blood flow and reverses the clinical picture in most symptomatic cases.

Conclusions. Although classically defined as a disease of a low-lying conus medullaris, the pathophysiology of TCS is much more complex and is dependent on a structural abnormality, with concomitant altered metabolic and vascular sequelae. Given the complex mechanisms underlying TCS, it is not surprising that the radiological criteria do not adequately address all presentations of the disease.

Neurosurg Rev (2010) 33:271–285. DOI 10.1007/s10143-010-0266-5

The exact pathogenesis of syringomyelia associated with Chiari type 1 malformation is unknown, although a number of authors have reported their theories of syrinx formation. The purpose of this review is to understand evidences based on the known theories and to create a new hypothesis of the pathogenesis. We critically review the literatures on clinicopathological, radiological, and clinical features of this disorder.

The previously proposed theories mainly focused on the driven mechanisms of the cerebrospinal fluid (CSF) into the spinal cord. They did not fully explain radiological features or effects of surgical treatment such as shunting procedures.

Common findings of the syrinx in clinicopathological studies were the communication with the central canal and extracanalicular extension to the posterior gray matter. Most of the magnetic resonance imaging studies demonstrated blockade and alternated CSF dynamics at the foramen magnum, but failed to show direct communication of the syrinx with the CSF spaces.

Pressure studies revealed almost identical intrasyrinx pressure to the subarachnoid space and decreased compliance of the spinal CSF space.

Recent imaging studies suggest that the extracellular fluid accumulation may play an important role. The review of evidences promotes a new hypothesis of syrinx formation. Decreased absorption mechanisms of the extracellular fluid may underlie the pathogenesis of syringomyelia. Reduced compliance of the posterior spinal veins associated with the decreased compliance of the spinal subarachnoid space will result in disturbed absorption of the extracellular fluid through the intramedullary venous channels and formation of syringomyelia.

J Neurosurg Pediatrics 5:474-478, 2010. DOI: 10.3171/2010.1.PEDS09218

The optimal surgical management of Chiari malformation (CM) is evolving. Evidence continues to accrue that supports decompression without duraplasty as an effective treatment to achieve symptomatic relief and anatomical decompression. The risks and benefits of this less invasive operation need to be weighed against decompression with duraplasty.

Methods. The authors performed a retrospective review of all CM decompressions from 2003 to 2007. All operations were performed by a single surgeon at a single institution. Data were analyzed for outcome, postoperative morbidity, and recurrence.

Results. Of 121 unique patients, 56 underwent posterior fossa decompressions without duraplasty (PFD) and 64 patients underwent posterior fossa decompressions with duraplasty (PFDD). Of the 56 PFD patients, 7 (12.5%) needed a subsequent PFDD for symptomatic recurrence. Of the 64 patients who underwent a PFDD, 2 (3.1%) needed a repeated PFDD for symptomatic recurrence. Patients treated with PFDD had an average operative time of 201 minutes in contrast to 127 minutes for those who underwent PFD (p = 0.0001). Patients treated with PFDD had average hospital stays of 4.0 days, whereas that for patients treated with PFD was 2.7 days (p = 0.0001). While in the hospital, patients treated with PFDD used low-grade narcotics, intravenous narcotics, muscle relaxants, and antiemetic medications at statistically significant differing rates.

Conclusions. While PFD was associated with a higher rate of recurrent symptoms requiring repeated decompression, this may be justified by the significantly lower morbidity rate. Clearer delineation of the trade-off between morbidity and recurrence may be used to help patients and their families make decisions regarding care.

Neurosurgery: February 2010 – Volume 66 – Issue 2 – p 368–375. doi: 10.1227/01.NEU.0000363858.17782.82

Microsurgical and endoscopic colloid cyst excision differ with regard to operative time, length of hospital stay, and extent of resection.

METHODS: A retrospective review of a single surgeon’s microsurgical colloid cyst resection in 10 consecutive patients was performed. Cyst size, hydrocephalus, symptoms, operative time, postoperative stay, complications, and objective testing of memory, concentration, calculation, and attention (cognition), along with performance at job, were noted.

RESULTS: All 10 patients had complete excision. Mean cyst size, mean operative time, and median postoperative stay were 1.6 cm, 124 minutes, and 3.5 days respectively. The mean operative time from cyst visualization to complete excision was 18 minutes. Follow-up ranged from 6 to 111 months (mean, 49.5 months). There were no recurrences; symptoms (headache, visual and balance problems) improved significantly in 70%. Postoperative cognitive performance, including memory, was the same in 8 patients (5 of whom had preoperative memory problems) and worse in 2 patients who had no preoperative memory problems. The bone flap was removed in 1 patient for wound dehiscence. Hemiparesis in another patient, seen immediately after surgery, completely resolved before discharge. One patient with loculated ventricles and multiple previous shunt revisions had unresolved hydrocephalus after cyst excision.

CONCLUSION: We report the very short operative times and postoperative stay for microsurgery, which are comparable to some endoscopic series. We also report results of objective tests of cognitive performance. With adoption of a callosal incision of 1 cm or less, meticulous dissection around the fornix, and complete excision, acceptable long-term cognitive function and functional performance were achieved. Our results support the microsurgical approach. A larger sample size can more conclusively establish whether it should be chosen over the endoscopic technique.

Acta Neurochir (2010) 152:213–219. DOI 10.1007/s00701-009-0427-x

With the frequent use of magnetic resonance imaging (MRI), patients with subtle and diffuse symptoms due to small syrinx cavities increasingly present to neurosurgical care. In this respect, a dilated central canal, hydromyelia, must be separated from patients with true syringomyelia with an underlying disorder, as they do not share clinical and radiological features. We hypothesize that a differentiation of these two entities with distinct diagnostic tools is possible.

Methods To describe the entity of hydromyelia, we excluded all patients from the syringomyelia database (n=142) with any obvious cause of a syringomyelia, any objective neurological deficits on clinical examination, pathological results on electrophysiological monitoring (SSEP, MEP, silent periods) or a widening of the spinal cord cavity of more than 6 mm on MRI [routine acquisitions with FLAIR, T1/T2-weighted images, Cine and CISS (constructive interference in steady-state) studies]. Life quality was assessed through SF-36 questionnaires and an individualized questionnaire for the clinical history, pain and alternative therapies.

Results Forty patients (15 males/25 females) matched the criteria of a hydromyelia. With a mean age of 36.7 years (range 11–62), they almost all presented with pain (79%) or dysaesthesia of the limbs, with some having been an incidental finding (10%). Over a follow-up time of 36.9 months (range 6–93) there was no neurological or radiological deterioration.

Conclusions Patients with a hydromyelia do not share clinical or radiological characteristics with patients harbouring a true syringomyelia. As hydromyelia does not represent a disease with an underlying pathology, no clinical or radiological progression has been seen. With sophisticated diagnostic tools to rule out any pathology this subset of patients can be identified.

Childs Nerv Syst (2010) 26:163–172.DOI 10.1007/s00381-009-0952-1

Purpose Middle fossa arachnoid cysts (MFAC) are a relatively common, benign pathology that pose a therapeutic challenge for both symptomatic and asymptomatic patients. The optimal surgical strategy and indication to treat are still debated by neurosurgeons. We reviewed our experience and results in a group of patients treated with endoscopic fenestration with the aim to assess indications to treat and clinical and neuroradiological results. Methods The data on 40 patients operated with endoscopic fenestration for MFAC in two centres, “Anna Meyer” Children’sHospital, Florence, Italy, and Royal Liverpool Children’s Hospital “Alder Hey”, Liverpool, UK, between 2001 and 2007 were retrospectively reviewed with prospective followup. We analysed clinical and neuroradiological presentation, indications to treat, surgical technique, complications, and clinical and neuroradiological follow-up. Results There were 30 males and ten females: mean age, 7.8 years; mean follow-up, 21 months. The neuronavigation system was used in 12 patients in the English cohort. Thirty-seven patients (92.5%) had a satisfactory clinical outcome. The cyst was reduced in size or completely disappeared in 29 patients (72.5%). There was no death or significant morbidity associated with the procedure. Four patients required further surgical treatment. Four patients experienced a post-traumatic intracystic bleeding after surgery. Conclusion Compared to microsurgical fenestration and cyst shunting, our experience with endoscopic fenestration was as effective and safe but less invasive. Each case must be assessed with its individual characteristics to define the optimal surgical strategy. Successful treatment may not reduce the risk of post-traumatic head injury haemorrhage.

Childs Nerv Syst (2010) 26:155–162. DOI 10.1007/s00381-009-0977-5

The optimal surgical management of sylvian arachnoid cysts is debated. We present our experience in children who were treated endoscopically, focusing on the limits and complications of this approach.

Materials and methods Seventeen children with a temporosylvian arachnoid cyst have been treated using a purely temporal endoscopic approach.

Results In all but one case, the recognition of anatomical landmarks was obtained at the insertion of the endoscope. In one child, the orientation and opening of the basal cisterns were more difficult due to the thickness and opacity of the membranes. Nevertheless, it was possible to perform the cysto-cisternostomy endoscopically in all children with several stomies in 13. In one child, a venous bleeding occurred. There were no other intraoperative complications. There were no postoperative cerebrospinal fluid leaks. In two patients, a symptomatic subdural collection developed which required a transient subdural-peritoneal shunt. No subdural collection was noted on a delayed follow-up (mean, 23 months). Preoperative symptoms related to the mass effect exerted by the cyst resolved in all children. Two children presented a recurrence, 12 and 20 months after endoscopic surgery, respectively. At the redo-endoscopy, the stomies were found to be closed. Their reopening resulted in the disappearance of the symptoms.

Conclusions An endoscopic approach can be used safely in the management of sylvian arachnoid cysts. An effective opening of the deep arachnoid membranes into the basal cisterns could be performed in all patients with the resolution of the preoperative symptoms. However, the long-term efficacy of the stoma needs to be assessed.

REV NEUROL 2009; 49: 630-2

Introduction. The vascular compression of a nerve is known to be the most important cause of idiopathic trigeminal neuralgia (ITN) by most authors. However, several cases of skull base deformities in patients with ITN have been reported in our bibliographic review. Aim. To compare the existence of platybasia between a group of patients with ITN and a randomized control group.

Subjects and methods. Twenty-five patients with ITN and twenty-five control subjects were X-rayed and their basal angles were measured and compared.

Results. The basal angle measured to investigate the existence of platybasia is significantly greater in the ITN group than in the control group. Platybasia was found in 10 patients with ITN. However, only two cases of platybasia were reported in the control group. Therefore in our study we have found that the incidence of platybasia in patients with ITN is significantly increased.

Conclusion. Our data demonstrated that platybasia has an important role in the pathogenesis of the ITN by altering the normal anatomy of the nerves and vessels within the posterior fossa

J Neurosurg Pediatrics 4:050360–500420, 2009.(DOI: 10.3171/2009.7.PEDS0994)

Sinus pericranii (SP) is a rare venous varix in an extracranial location connected to the intracranial venous system. The aim of this retrospective study was to report on 16 pediatric cases of SP with consideration of the preoperative evaluation of surgical risk.

Methods. The study population consisted of 10 patients who had undergone surgery for SP and 6 patients with concomitant craniosynostosis and SP. The mean age of the patients at presentation was 3.7 years. To identify characteristics of SP with high operative risk, 8 cases in this report and 11 previously reported cases of SP with sufficient information were categorized on the basis of the number and size of SP, the number and size of transcranial channels, the venous drainage type, and the amount of blood loss. Hemorrhage amounts were classified into 3 grades based on the description of intraoperative blood loss.

Results. Sinus pericranii not associated with craniosynostosis were resected without any postoperative morbidity. Sinus pericranii associated with craniosynostosis were preserved. After craniofacial reconstruction, 2 cases of SP with craniosynostosis regressed, completely in one patient and partially in another. These 2 patients with SP were confirmed to have compromised intracranial sinus before craniofacial reconstruction. Among a total of 19 patients, multiplicity or size (> 6 cm) of SP (p = 0.036) and multiplicity (> 3) or size (> 3 mm) of transcranial channels (p = 0.004) was associated with more severe hemorrhage grade. Sinus pericranii with peripheral venous drainage (drainer type) was not associated with hemorrhage grade after classification into 3 grades (p = 0.192). However, all 3 cases of SP with massive Grade 3 hemorrhage were the drainer type. Hemorrhage grade was correlated with the number of risk factors for SP (r = 0.793, p < 0.001).

Conclusions. Three risk factors of SP and the presence of compromised intracranial sinus are markers for high-risk SP. “Squeezed-out sinus syndrome” is suggested as a concept for SP associated with compromised intracranial sinus, mainly caused by craniosynostosis. Sinus pericranii in squeezed-out sinus syndrome probably serves as a crucial alternative to venous drainage of the brain with intracranial venous compromise. Conservative treatment for such patients with SP is recommended.

Neurosurg Focus 27 (5):E14, 2009.DOI: 10.3171/2009.9.FOCUS09165

Multiple pathophysiological mechanisms have been proposed for the increased intracranial pressure observed in idiopathic intracranial hypertension (IIH). The condition is well characterized, with intractable headaches, visual obscurations, and papilledema as dominant features, mainly affecting obese women. With the advent of MR venography and increased use of cerebral angiography, there has been recent emphasis on the significant number of patients with IIH found to have associated nonthrombotic dural venous sinus stenosis. This has led to a renewed interest in endovascular stenting as a treatment for IIH. However, the assumption that venous stenosis leads to a high pressure gradient that decreases CSF resorption through arachnoid villi requires further evidence.

In this paper, the authors analyze the published results to date of dural venous sinus stenting in patients with IIH. They also present a case from their institution for illustration.

The pathophysiological mechanism in IIH requires further elucidation, but venous sinus stenosis with subsequent intracranial hypertension appears to be an important mechanism in at least a subgroup of patients with IIH. Among these patients, 78% had complete relief or improvement of their main presenting symptoms after endovascular stenting.

Resolution or improvement in papilledema was seen in 85.1% of patients.

Endovascular stenting should be considered whenever venous sinus stenosis is diagnosed in patients with IIH.

Childs Nerv Syst. DOI 10.1007/s00381-009-0977-5

The optimal surgical management of sylvian arachnoid cysts is debated. We present our experience in children who were treated endoscopically, focusing on the limits and complications of this approach.

Materials and methods: Seventeen children with a temporo- sylvian arachnoid cyst have been treated using a purely temporal endoscopic approach.

Results: In all but one case, the recognition of anatomical landmarks was obtained at the insertion of the endoscope. In one child, the orientation and opening of the basal cisterns were more difficult due to the thickness and opacity of the membranes. Nevertheless, it was possible to perform the cysto-cisternostomy endoscopically in all children with several stomies in 13. In one child, a venous bleeding occurred. There were no other intraoperative complications. There were no postoperative cerebrospinal fluid leaks. In two patients, a symptomatic subdural collection developed which required a transient subdural-peritoneal shunt. No subdural collection was noted on a delayed follow-up (mean, 23 months). Preoperative symptoms related to the mass effect exerted by the cyst resolved in all children. Two children presented a recurrence, 12 and 20 months after endoscopic surgery, respectively. At the redo-endoscopy, the stomies were found to be closed. Their reopening resulted in the disappearance of the symptoms.

Conclusions: An endoscopic approach can be used safely in the management of sylvian arachnoid cysts. An effective opening of the deep arachnoid membranes into the basal cisterns could be performed in all patients with the resolution of the preoperative symptoms. However, the long-term efficacy of the stoma needs to be assessed.

Neurosurg Rev (2009) 32:465–470. DOI 10.1007/s10143-009-0214-4

To restore the cerebrospinal fluid (CSF) flow at the craniocervical junction in Chiari I malformation (CM-I), most surgeons practice a suboccipital craniectomy with duraplasty. To reduce the risk of CSF leak, a dura splitting decompression is created removing only the dural outer layer. We report on a series of 11 patients with CM-I (five with syringomyelia) operated on between 2000 and 2007 using this technique. Neurological examination and cerebro-spinal MRI scan were performed before and after surgery. Symptoms improved completely in six patients. Headaches and cervicalgias disappeared for all patients. Dizziness and paresthesia in the upper limb remained unchanged for three and two patients, respectively. We observed no complications such as CSF leak, meningocele, or meningitis. Postoperative MRI scan showed a significant craniocervical decompression in ten patients. Four patients had a new cisterna magna. Two syringomyelias completely disappeared, two decreased, and one was stable. Dural splitting can be practiced to treat CM-I. Clinical results are similar to the other techniques with less complications. Radiological findings show satisfying posterior fossa decompression.

Child’s Nervous System

Purpose Middle fossa arachnoid cysts (MFAC) are a relatively common, benign pathology that pose a therapeutic challenge for both symptomatic and asymptomatic patients. The optimal surgical strategy and indication to treat are still debated by neurosurgeons. We reviewed our experience and results in a group of patients treated with endoscopic fenestration with the aim to assess indications to treat and clinical and neuroradiological results.
Methods The data on 40 patients operated with endoscopic fenestration for MFAC in two centres, “Anna Meyer” Children’s Hospital, Florence, Italy, and Royal Liverpool Children’s Hospital “Alder Hey”, Liverpool, UK, between 2001 and 2007 were retrospectively reviewed with prospective follow-up. We analysed clinical and neuroradiological presentation, indications to treat, surgical technique, complications, and clinical and neuroradiological follow-up.
Results There were 30 males and ten females: mean age, 7.8 years; mean follow-up, 21 months. The neuronavigation system was used in 12 patients in the English cohort. Thirty-seven patients (92.5%) had a satisfactory clinical outcome. The cyst was reduced in size or completely disappeared in 29 patients (72.5%). There was no death or significant morbidity associated with the procedure. Four patients required further surgical treatment. Four patients experienced a post-traumatic intracystic bleeding after surgery.
Conclusion Compared to microsurgical fenestration and cyst shunting, our experience with endoscopic fenestration was as effective and safe but less invasive. Each case must be assessed with its individual characteristics to define the optimal surgical strategy. Successful treatment may not reduce the risk of post-traumatic head injury haemorrhage.
DOI 10.1007/s00381-009-0952-1