Neurological manifestations of intracranial dural arteriovenous malformations

The authors describe their experience with four cases of dural arteriovenous malformation (AVM) which led them to analyze the clinical aspects of these lesions in an attempt to understand their pathophysiology. An additional 191 previously reported cases of dural AVM's were reviewed with special attention to the mechanism of intradural, central, and peripheral nervous system manifestations. Apart from the peripheral cranial nerve symptoms, which are most likely due to arterial steal, the central nervous system (CNS) symptoms appear to be related to passive venous hypertension and/or congestion. Generalized CNS symptoms can be related to cerebrospinal fluid malabsorption due either to increased pressure in the superior sagittal sinus, to venous sinus thrombosis, or to meningeal reaction resulting from minimal subarachnoid hemorrhages. These phenomena are not related to the anatomical type of venous drainage. On the other hand, focal CNS symptoms are specifically indicative of cortical venous drainage. Seizures, transient ischemic attacks, motor weakness, and brain-stem and cerebellar symptoms can be encountered depending on the territory of the draining vein or veins. Therefore, the localizing value of focal CNS symptomatology relates to the venous territory and not to the nidus or to the arterial supply characteristics of dural AVM's. Furthermore, the venous patterns of various dural AVM's at the base of the skull are expressed by differences in their clinical presentation. Dural AVM's of the floor of the anterior cranial fossa and of the tentorium are almost always drained by the cortical veins and, therefore, have a high risk of intradural bleeding. The remarkable similarities in the manifestations of dural and brain AVM's and the differences in the manifestations of dural and spinal dural AMV's are pointed out. High-quality angiograms and a multidisciplinary approach to the study of dural AVM's will provide the best understanding of their symptoms and, therefore, the most appropriate treatment strategy.

Measurement of intraoperative brain surface deformation under a craniotomy

OBJECTIVE

Several causes of spatial inaccuracies in image-guided surgery have been carefully studied and documented for several systems. These include error in identifying the external features used for registration, geometrical distortion in the preoperative images, and error in tracking the surgical instruments. Another potentially important source of error is brain deformation between the time of imaging and the time of surgery or during surgery. In this study, we measured the deformation of the dura and brain surfaces between the time of imaging and the start of surgical resection for 21 patients.

METHODS

All patients underwent intraoperative functional mapping, allowing us to measure brain surface motion at two times that were separated by nearly an hour after opening the dura but before performing resection. The positions of the dura and brain surfaces were recorded and transformed to the coordinate space of a preoperative magnetic resonance image, using the Acustar surgical navigation system (manufactured by Johnson & Johnson Professional, Inc., Randolph, MA) (the Acustar trademark and associated intellectual property rights are now owned by Picker International, Highland Heights, OH). This system performs image registration with bone-implanted markers and tracks a surgical probe by optical triangulation.

RESULTS

The mean displacements of the dura and the first and second brain surfaces were 1.2, 4.4, and 5.6 mm, respectively, with corresponding mean volume reductions under the craniotomy of 6, 22, and 29 cc. The maximum displacement was greater than 10 mm in approximately one-third of the patients for the first brain surface measurement and one-half of the patients for the second. In all cases, the direction of brain shift corresponded to a "sinking" of the brain intraoperatively, compared with its preoperative position. Analysis of the measurement error revealed that its magnitude was approximately 1 to 2 mm. We observed two different patterns of the brain surface deformation field, depending on the inclination of the craniotomy with respect to gravity. Separate measurements of brain deformation within the closed cranium caused by changes in patient head orientation with respect to gravity suggested that less than 1 mm of the brain shift recorded intraoperatively could have resulted from the change in patient orientation between the time of imaging and the time of surgery.

CONCLUSION

These results suggest that intraoperative brain deformation is an important source of error that needs to be considered when using surgical navigation systems.

Increased responses in trigeminocervical nociceptive neurons to cervical input after stimulation of the dura mater

Pain referral and spread in headache patients may be attributed to a sensitization of central nociceptive neurons with an increased excitability to afferent input. We investigated if noxious dural stimulation evokes sensitization of second-order neurons that leads to an increased responsiveness to stimulation of cervical afferents. Recordings were made from 29 nociceptive neurons in the C2 dorsal horn of the rat that received convergent synaptic input from trigeminal and cervical afferents. Trigeminal afferents of the supratentorial dura mater were activated by mustard oil (MO) and the responses of second-order neurons to stimulation of the greater occipital nerve (GON) were studied before and after dural stimulation. Projection sites to the contralateral thalamus were determined by antidromic stimulation. After dural application with MO, mechanical thresholds of the dura significantly decreased (P < 0.05) and an enlargement of the trigeminal and cervical cutaneous mechanoreceptive fields was observed in 71% of neurons. The responses to noxious mechanical stimulation of deep paraspinal muscles increased after MO application (P < 0.001). Similarly, an increase in the excitability to electrical stimulation of the GON was observed in C-fibre responses (P < 0.001). These results suggest that stimulation of nociceptive afferent C-fibres of the dura mater leads to a sensitization of second-order neurons receiving cervical input. This mechanism might be involved in the referral of pain from trigeminal to cervical structures and might contribute to the clinical phenomena of cervical hypersensitivity in migraine and cluster headache. Understanding this interaction is likely to be pivotal in characterizing the physiology of treatment with manipulations involving cervical input, such as GON injection.

Physical model simulations of brain injury in the primate

Diffuse brain injuries resulting from non-impact rotational acceleration are investigated with the aid of physical models of the skull-brain structure. These models provide a unique insight into the relationship between the kinematics of head motion and the associated deformation of the surrogate brain material. Human and baboon skulls filled with optically transparent surrogate brain tissue are subjected to lateral rotations like those shown to produce diffuse injury to the deep white matter in the brain of the baboon. High-speed cinematography captures the deformations of the grids embedded within the surrogate brain tissue during the applied load. The overall deformation pattern is compared to the pathological portrait of diffuse brain injury as determined from animal studies and autopsy reports. Shear strain and pathology spatial distributions mirror each other. Load levels and resulting surrogate brain tissue deformations are related from one species to the other. Increased primate brain mass magnified the strain amplified without significantly altering the spatial distribution. An empirically-derived value for a critical shear strain associated with the onset of severe diffuse axonal injury in primates is determined, assuming constitutive similarity between baboon and human brain tissue. The primate skull physical model data and the critical shear strain associated with the threshold for severe diffuse axonal injury were used to scale data obtained from previous studies to man, and thus derive a diffuse axonal injury tolerance for rotational acceleration for humans.

Redefined role of angiogenesis in the pathogenesis of dural arteriovenous malformations

To investigate the role of angiogenesis in the pathogenesis of dural arteriovenous malformations (AVMs), 40 rats underwent common carotid artery-external jugular vein (CCA-EJV) anastomosis, bipolar coagulation of the vein draining the transverse sinus, and sagittal sinus thrombosis to induce venous hypertension. Fifteen rats underwent a similar surgical procedure, but venous hypertension was not induced. The 55 rats were divided into seven groups. Four groups, each containing 10 rats, underwent induced venous hypertension. The other three groups, each containing five rats, did not undergo induced venous hypertension. After 1, 2, or 3 weeks, dura mater was obtained from one group of hypertensive rats and from one group of nonhypertensive rats and was assayed for angiogenic activity (rabbit cornea bioassay). The remaining group of 10 hypertensive rats was not assayed to determine if sampling affected dural AVM formation. Unlike rats without CCA-EJV anastomosis, rats with CCA-EJV anastomosis had significantly increased postoperative sagittal sinus pressures (p < 0.0001). Mean angiogenesis indices were significantly greater in rats with venous hypertension than in rats without venous hypertension (p = 0.004). Dural AVMs formed in 42% of the 55 rats and facial AVMs formed in 51%. Angiogenic activity correlated positively with venous hypertension (p = 0.74). Development of dural AVMs correlated positively with both venous hypertension (p = 0.0009) and angiogenic activity (p = 0.04). These data indicate that venous hypertension may induce angiogenic activity either directly or indirectly by decreasing cerebral perfusion and increasing ischemia, and that dural AVM formation may be the result of aberrant angiogenesis.

Differential modulation of nociceptive dural input to [hypocretin] orexin A and B receptor activation in the posterior hypothalamic area

The novel neuropeptides orexin A and B are selectively synthesised in the lateral and posterior hypothalamus and are involved in hypothalamic regulation of autonomic and neuroendocrine functions. Recent findings point also to a role in nociception. As the posterior hypothalamus is involved in the central modulation of nociception we studied the effects of hypocretin/orexin receptor activation in the posterior hypothalamic area (PH) of the rat on dural nociceptive input. Orexins were microinjected into the PH and the effects on responses of neurones in the caudal trigeminal nucleus studied. Injection of orexin A decreased the A- and C-fibre responses to dural electrical stimulation as well as spontaneous activity. Responses to noxious thermal stimulation of the facial skin were also decreased by orexin A. Injection of orexin B into the PH, however, elicited increased responses to dural stimulation in A- and C-fibre responses and resulted in increased spontaneous activity. Responses to facial thermal stimulation were also increased by orexin B. Control injection of saline into the PH had no significant effect. The results show a differential modulation of dural nociceptive input by orexin A and B receptor activation in the PH. The results support the role of the PH in the nociceptive processing of meningeal input. As both peptides are also involved in hypothalamic regulation of neuroendocrine and autonomic functions, orexinergic mechanisms in the PH may provide a link for endocrine and autonomic changes as well as nociceptive phenomena seen in primary headache disorders.

Episodic dural stimulation in awake rats: a model for recurrent headache

OBJECTIVES

To model, in rats, the development of chronic trigeminal nociceptive hypersensitivity seen in patients with recurrent headache.

BACKGROUND

Pathophysiology studies suggest that patients with recurrent migraine headache experience repeated bouts of dural nociceptor activation. In some patients, the severity and frequency of headache attacks increase over time. Patients with recurrent headache are hypersensitive to nitric oxide donors, such as glyceryl trinitrate (GTN). Current trigeminal pain models do not reflect the repeated episodic nature of dural nociceptor activation in patients with recurrent headache. Repeated nociceptor activation creates long-lasting changes in the periphery and brain due to activity-dependent neuronal plasticity. An animal model of repeated activation of dural nociceptors will facilitate the study of the physiological changes caused by repeated, episodic pain and the factors important for the transition of episodic to chronic migraine.

METHODS

We induced dural inflammation by infusing an inflammatory soup (IS) through a cannula on the dura in awake behaving rats. This was repeated 3 times per week for up to 4 weeks. Periorbital pressure sensory testing was used to monitor the change in trigeminal sensitivity. Rats were challenged with GTN to test the hypothesis that many dural stimulations are required to model the hypersensitivity of migraine patients. Quantitative trigeminal sensory testing and microdialysis in the trigeminal nucleus caudalis (TNC) were used to measure GTN hypersensitivity.

RESULTS

Multiple infusions of IS (>8), over weeks, induced a long-lasting decrease in periorbital pressure thresholds that lasted >3 weeks after the last infusion. In contrast, IS infusion in IS-naive rats and those that received 3 IS infusions produced only short-lasting decreases in periorbital pressure thresholds. Rats that received more than 8 IS infusions showed a marked increase in their neurochemical and behavioral responses to GTN. In these rats, GTN induced a decrease in periorbital von Frey thresholds that lasted >5 hours. In contrast, in rats that received only 3 IS infusions, GTN caused a threshold decrease for 1.5 hour. In vivo microdialysis in the TNC showed that GTN increased extracellular glutamate levels in rats with more than 8 IS infusions to 7.7 times the basal levels. In IS-naive rats and those that received only 3 IS infusions, the extracellular glutamate levels rose to only 1.7 and 1.9 times the basal level, respectively.

CONCLUSIONS

Repeated IS stimulation of the dura produces a chronic state of trigeminal hypersensitivity and potentiates the response to GTN. This hyperresponsiveness outlasts the last IS infusion and is the basis of our rat model of recurrent headache. This model can be used to study the changes in the brain and periphery induced by repeated trigeminovascular nociceptor activation and has the potential to elucidate the mechanisms for the transition of episodic to chronic headache.

Neurogenically mediated plasma extravasation in dura mater: effect of ergot alkaloids. A possible mechanism of action in vascular headache

C-fiber-dependent neurogenic plasma extravasation developed in the dura mater but not the brain after electric stimulation of the rat trigeminal ganglion or after chemical stimulation of perivascular axons with intravenous capsaicin, a drug that depolarizes sensory nerve fibers. C-fiber-independent extravasation also developed in this tissue after intravenous injections of substance P or neurokinin A (two constituents of unmyelinated C fibers) and after serotonin, bradykinin, or allergic challenge in presensitized animals. Intravenous dihydroergotamine or ergotamine tartrate, in doses similar to those used to treat migraine and cluster headache, prevented the stimulation-induced leakage of plasma proteins within the dura mater. Not unexpectedly, the acute administration of methysergide, a drug effective in the prophylactic treatment of headache, was inactive in this acute model. Neither acute nor chronic administration of propranolol affected stimulation-induced leakage of plasma protein. These results demonstrate that neurogenic inflammation develops within the dura mater in the rat and that ergot alkaloids prevent the process by a C-fiber-dependent mechanism.

Spinal cord arteriovenous shunts: from imaging to management

Spinal cord arteriovenous shunts (SCAVSs) are either fistulas or niduses that can be separated in four different groups according to their localization and relationship to the dura. Paraspinal AVSs are located outside the spine and are responsible for neurological symptoms because of cord compression by ertatic veins, venous congestion or arterial steal. Epidural shunts are located in the epidural space and drain in epidural veins with secondary intradural congestion. Dural shunts are embedded in the dura, produce a cord venous myelopathy after draining through veins that either pierce the dura far from a nerve root or accompany a nerve root. Intradural shunts affect the cord, the roots or the filum. Additionally, they can be classified according to their potential relationships with genetics, vascular biological features and angiogenesis into genetic hereditary lesions (hereditary hemorrhagic telangiectasia), genetic non-hereditary lesions (multiple lesions with metameric links) and single lesions (AVMs or micro AVFs). MRI and MRA are able to visualise SCAVS early after the onset of clinical symptoms. The type of shunt and its localization may remain difficult to be precise. Angiography remains the gold standard for analysis of the anatomical, morphological and architectural features necessary for therapeutic decisions in both paediatric and adult populations. In our series, embolisation is chosen in first intention whatever the type of shunt responsible for the clinical symptoms and glue is preferably used. In paraspinal, dural or epidural arteriovenous shunts, the goal of treatment should be complete closure of the shunt. A complete cure by embolization is rather easily achieved in paraspinal lesions. Failure of endovascular therapy in dural or epidural shunts must bring the patient to surgery. The prognosis of most intradural shunts seems better than previously thought, even after haemorrhage. In intradural spinal cord arteriovenous shunts, embolisation targeted towards the portions of the malformation felt to be responsible for the symptoms (venous congestion) or pointing to the point of rupture (false aneurysms) of the malformation, allows restoration of a new hemodynamic equilibrium between the malformation and the cord itself. Such targeted treatment offers long-term stabilisation or improvement to patients suffering from SCAVSs and good protection against (re) haemorrhages, with an acceptable morbidity. Cure of the shunt is not imperative to obtain these satisfactory outcomes. The clinical results obtained by such management compare favourably with those obtained by neurosurgery.

Response Properties of Dural Nociceptors in Relation to Headache

Single-unit electrophysiological recording studies have examined the activity of sensory neurons in the trigeminal ganglion that innervate the intracranial meninges to better understand their possible role in headache. A key question is whether the meningeal sensory neurons are similar to nociceptive neurons in other tissues or, alternatively, whether they have unique properties that might be of significance for headache pathogenesis and drug therapy. Such studies have indeed found that the intracranial dura is innervated by neurons that exhibit properties characteristic of nociceptors in other tissues, including chemosensitivity and sensitization. This sensitization, consisting of an enhanced responsiveness to mechanical stimuli, might be relevant to symptoms that are characteristic of certain headaches that indicate the presence of an exaggerated intracranial mechanosensitivity. Studies that examined whether the anti-migraine agent sumatriptan might inhibit this sensitization (in addition to its well-known inhibition of neurotransmitter release) found that it had no inhibitory effect but rather produced a calcium-dependent discharge, which might account for the initial worsening of headache that can follow sumatriptan administration. In studies that examined the effects of vasodilator agents, nitroprusside produced mixed effects on mechanosensitivity, whereas calciton gene-related peptide (CGRP) had no effect on either spontaneous or mechanically evoked discharge. These results call into question the role of vasodilation in headache and suggest that the role of CGRP in headache may be through its action as a central neurotransmitter rather than through vasodilation and activation of meningeal nociceptors. In general, studies of meningeal sensory neurons have not found evidence of unique properties that distinguish them from nociceptive neurons in other tissues. Ultimately the distinctive clinical characteristics of headache may prove to be related not so much to any differences in the intrinsic molecular or cellular properties of the meningeal sensory neurons but rather to the distinctive properties of the tissue that they innervate.

A neurohistochemical blueprint for pain-induced loss of appetite

A common complaint among pain patients is that they lose their appetite. These accounts are anecdotal, however, and the neural mechanism underlying pain-induced loss of appetite remains unknown. In this study, we documented the occurrence of appetite loss in patients under migraine attack and investigated the neuronal substrate of pain-induced anorexia in our animal model of intracranial pain. We found that loss of appetite during the migraine attack in humans coincided strongly with the onset and duration of the head pain in 32/39 cases, and that brief noxious stimulation of the dura in conscious rats produced a transient suppression of food intake. Mapping of neuronal activation in the rat showed that noxious dural stimulation induced a 3- to 4-fold increase in the number of Fos-positive neurons in medullary dorsal horn areas that process nociceptive signals (laminae I, V) and in parabrachial and hypothalamic neurons positioned to suppress feeding behavior. In the parabrachial area, activated neurons were localized in the superior-lateral subnucleus, and 40% of them expressed the mRNA encoding the anorectic neuropeptide cholecystokinin. In the hypothalamus, activated Fos-positive neurons were found in the dorsomedial area of the ventromedial nucleus, and 76% of them expressed the mRNA for cholecystokinin type-B receptor. Based on these findings, we suggest that at least one of several groups of hypothalamic neurons that normally inhibit appetite in response to metabolic cues is positioned to mediate the suppression of food intake by pain signals.

C3-6 laminoplasty takes over C3-7 laminoplasty with significantly lower incidence of axial neck pain

Five-lamina (C3-7) procedure is the most popular cervical laminoplasty and there have been no studies on the most appropriate number of laminae to be opened. We prospectively reduced the range of laminoplasty from C3-7 to C3-6 in 2002 and compared the outcome of C3-6 laminoplasty (n=37) to that of C3-7 laminoplasty (n=28). In both groups, neurological gain was satisfactory, radiographic changes were minimal, and postoperative MRI indicated sufficient expansion of the dura and the spinal cord. Average operating period was significantly shorter, and length of the operative wound was significantly less in the C3-6 group than in the C3-7 group. Postoperative axial neck pain was significantly rarer after C3-6 laminoplasty than after C3-7 laminoplasty (5.4% vs. 29%, P=0.015). Due to its simplicity and various benefits, C3-6 laminoplasty is a promising alternative to conventional C3-7 laminoplasty for treatment of multisegmental compression myelopathy.

Tuberculum sellae meningiomas: functional outcome in a consecutive series treated microsurgically

OBJECTIVE

The objective of this study was to analyze a series of patients harboring a tuberculum sellae meningioma with regard to clinical presentation and long-term functional outcome.

METHODS

Data in a consecutive series of 62 patients harboring a tuberculum sellae meningioma treated microsurgically between 1990 and 2003 were retrospectively reviewed.

RESULTS

The mean age of the 46 women and 16 men enrolled in the study was 53 years (range = 29-81 years). The presenting symptom was visual compromise in 87.1% of the patients, and examination revealed decreased visual acuity in 79% and impaired visual fields in 64.5% of the patients. In addition, 14.5% of the patients had preoperative hormonal abnormalities. Simpson grades I and II resections, usually via a pterional approach, were achieved in 90.3% of the patients. Postoperatively, vision improved in 53.2%, remained unchanged in 29.8%, and deteriorated in 17.0% of the patients. The intraoperative finding predicting an unfavorable visual outcome was a thin atrophic optic nerve, encasement of the nerve, or tumor adhesion to its undersurface. Of the patients, 12.9% required permanent postoperative hormonal replacement. After a mean follow-up period of 6.0 years (range = 18 months-14 years), 88.7% of the patients resumed normal life activity and 2 recurrent tumors were observed (3.2%) and reoperated.

CONCLUSIONS

Preoperative magnetic resonance imaging provides reliable information with regard to dislocation of critical vascular structures. However, the relationship between optic nerves and tumors (eg, adhesion and encasement) affected postoperative results and can only be fully appreciated during microsurgery. Visual outcome may be improved by preserving the microvasculature supplying the optic apparatus.

Ventricular pressure monitoring during bilateral decompression with dural expansion

OBJECT

The management of massive brain swelling remains an unsolved problem in neurosurgery. Despite newly developed medical and pharmacological therapy, the rates of mortality and morbidity caused by massive brain swelling remain high. According to many recent reports, surgical decompression with dural expansion is superior to medical management in patients with massive brain swelling. To show the quantitative effect of decompressive surgery on intracranial pressure (ICP), the authors performed a ventricular puncture and measured the ventricular ICP continuously during decompressive surgery and the postoperative period.

METHODS

Twenty patients with massive brain swelling who underwent bilateral decompressive craniectomy with dural expansion were included in this study. In all patients, ventricular puncture was performed at Kocher's point on the side opposite the massive brain swelling. The ventricular puncture tube was connected to the continuous monitor via a transducer device. The ventricular pressure was monitored continuously, during the bilateral decompressive procedures and postoperative period. The initial ventricular ICP was variable, ranging from 16 to 65.8 mm Hg. Immediately after the bilateral craniectomy, the mean ventricular ICP decreased to 50.2+/-16.6% of the initial ICP (range 5-51.5 mm Hg). Additional opening of the dura decreased the mean ICP by an additional 34.5% and reduced the ventricular pressure to 15.7+/-10.7% of the initial pressure (range 0-15 mm Hg). Ventricular pressure measured postoperatively in the neurosurgical intensive care unit was lowered to 15.1+/-16.5% of the initial ICP. The ventricular ICP trend in the first 24 hours after decompressive surgery was an important prognostic factor; if it was greater than 35 mm Hg, the mortality rate was 100%.

CONCLUSIONS

Bilateral decompression with dural expansion is an effective therapeutic modality in the control of ICP. To obtain favorable clinical outcomes in patients with massive brain swelling, early decision making and proper patient selection are very important.

Dura mater stimulates human adipose-derived stromal cells to undergo bone formation in mouse calvarial defects

Human adipose-derived stromal cells (hASCs) have a proven capacity to aid in osseous repair of calvarial defects. However, the bone defect microenvironment necessary for osseous healing is not fully understood. In this study, we postulated that the cell-cell interaction between engrafted ASCs and host dura mater (DM) cells is critical for the healing of calvarial defects. hASCs were engrafted into critical sized calvarial mouse defects. The DM-hASC interaction was manipulated surgically by DM removal or by insertion of a semipermeable or nonpermeable membrane between DM and hASCs. Radiographic, histologic, and gene expression analyses were performed. Next, the hASC-DM interaction is assessed by conditioned media (CM) and coculture assays. Finally, bone morphogenetic protein (BMP) signaling from DM was investigated in vivo using novel BMP-2 and anti-BMP-2/4 slow releasing scaffolds. With intact DM, osseous healing occurs both from host DM and engrafted hASCs. Interference with the DM-hASC interaction dramatically reduced calvarial healing with abrogated BMP-2-Smad-1/5 signaling. Using CM and coculture assays, mouse DM cells stimulated hASC osteogenesis via BMP signaling. Through in vivo manipulation of the BMP-2 pathway, we found that BMP-2 plays an important role in DM stimulation of hASC osteogenesis in the context of calvarial bone healing. BMP-2 supplementation to a defect with disrupted DM allowed for bone formation in a nonhealing defect. DM is an osteogenic cell type that both participates in and stimulates osseous healing in a hASC-engrafted calvarial defect. Furthermore, DM-derived BMP-2 paracrine stimulation appears to play a key role for hASC mediated repair.

Functional relationships between sensory nerve fibers and mast cells of dura mater in normal and inflammatory conditions

In this study, we have characterized the phenotype of mast cells in rat dura mater and their topological and functional relationships with C-fibers in normal and inflammatory conditions. Three mast cell populations with different size, morphology and localization were characterized by their content of specific neutral serine proteases. They showed immunoreactivity corresponding to rat mast cell protease I, rat mast cell protease II, or both proteases. Using confocal microscopy, all three mast cell types were observed in close apposition (distance less than 100 nm) to calcitonin gene-related peptide- and substance P-immunoreactive nerve fibers in both controls and rats infected with the nematode Nippostrongylus brasiliensis. After nematode infection or neonatal treatment with capsaicin, a large increase in the number of rat mast cell protease II-immunoreactive mast cells was found within dura mater segments (+1478% and +596%, respectively), without concomitant changes of rat mast cell protease I- or rat mast cell protease I/II-immunoreactive mast cells. Under both these conditions, the increase in mast cell number was accompanied by a significant increase in rat mast cell protease II level within tissue extracts (+281% after nematode infection and +36% after capsaicin treatment). The functional interaction of mast cells with sensory nerve fibers in the dura mater was assessed by evaluating [3H]histamine synthesis after administration of L-[3H]histidine, an index of mast cell activity. The H3 receptor agonist (R)-alpha-methylhistamine (15 mg/kg, i.p.) had no effect, but administration of the H3 receptor antagonist, thioperamide (10 mg/kg, i.p.), resulted in a significant increase of [3H]histamine synthesis (+62%). This effect was reduced in neonatal capsaicin-treated rats, but not completely suppressed (+35%), very likely because of partial denervation, as assessed by monitoring calcitonin gene-related peptide immunoreactivity. It is concluded that, in the dura mater, as in peripheral tissues, sensory nerve fibers and mast cells actively synthesizing and releasing histamine form a short inhibitory feedback loop involving prejunctional H3 receptors that could regulate the release of pro-inflammatory mediators, thus limiting the extent of inflammatory reactions.

Treatment of chronic subdural hematoma by burr-hole craniostomy in adults: influence of some factors on postoperative recurrence

BACKGROUND

The study was conducted to determine the causative factors in the postoperative recurrence (PR) of chronic subdural haematomas (CSDHs) and to evaluate the efficacy of surgery in adults enrolled in this trial.

METHODS

99 patients with 121 CSDHs, who were operated on between January 1999 and December 2001, were studied. We evaluated the PR rate related to anamnestic, clinical, surgical and neuroradiological imaging variables. In addition, we reviewed the number and the type of repeated operations, complications of surgery and the outcomes at one, three and 12 months.

FINDINGS

82.6% of lesions were successfully treated following the initial evacuation, and 95.9% of lesions following a second procedure. The PR rate was 14.9%. A significantly high PR rate was found to be associated with separated type, frontal base type, a midline displacement >5 mm and the presence of acute subdural clots in cranial base type on CT scans obtained within four days postsurgery. The interval from head trauma to initial surgery <60 days, the maximum width of subdural space >10 mm and massive collection of air in the subdural space tended to give a high PR rate. The PR rate associated with the homogeneous type of CSDHs was significantly low.Age, sex, cause of CSDH, anticoagulant therapy, preoperative neurological presentation, concomitant disease, variables on preoperative CT scans, and surgical factors such as the extent of the surgical procedure, use of drainage, duration and volume of drainage were not significantly associated with PR rate.

CONCLUSIONS

It is important to identify factors leading to a high or a low PR rate in the treatment of CSDHs because this may help to select appropriate surgical procedures and postoperative management to treat this condition efficiently.

Cranial Suture Regeneration Mitigates Skull and Neurocognitive Defects in Craniosynostosis

Craniosynostosis results from premature fusion of the cranial suture(s), which contain mesenchymal stem cells (MSCs) that are crucial for calvarial expansion in coordination with brain growth. Infants with craniosynostosis have skull dysmorphology, increased intracranial pressure, and complications such as neurocognitive impairment that compromise quality of life. Animal models recapitulating these phenotypes are lacking, hampering development of urgently needed innovative therapies. Here, we show that Twist1+/- mice with craniosynostosis have increased intracranial pressure and neurocognitive behavioral abnormalities, recapitulating features of human Saethre-Chotzen syndrome. Using a biodegradable material combined with MSCs, we successfully regenerated a functional cranial suture that corrects skull deformity, normalizes intracranial pressure, and rescues neurocognitive behavior deficits. The regenerated suture creates a niche into which endogenous MSCs migrated, sustaining calvarial bone homeostasis and repair. MSC-based cranial suture regeneration offers a paradigm shift in treatment to reverse skull and neurocognitive abnormalities in this devastating disease.

Colocalization of CGRP with 5-HT1B/1D receptors and substance P in trigeminal ganglion neurons in rats

Vasodilatation in the dura mater has been implicated in migraine pathogenesis. Anti-migraine triptan drugs block vasodilatation by binding to 5-HT1B/1D receptors localized on the peripheral sensory terminals and dural blood vessel smooth muscles. Previous studies suggest that calcitonin gene-related peptide (CGRP) released from Adelta-fibres plays a more important role than substance P (SP) released from C-fibres in inducing dural vasodilatation and that one of the antimigraine mechanisms of triptan drugs is inhibiting CGRP release. In the present study, the relationship between CGRP and 5-HT1B/1D receptors, and between CGRP and SP in the trigeminal ganglion neurons in rats was examined by double immunohistochemical staining. CGRP, 5-HT1B, 5-HT1D and SP-positive trigeminal ganglion neurons were all predominantly small and medium-sized. In the trigeminal ganglia, approximately 50% of CGRP-positive neurons were 5-HT1B positive. Similarly, approximately 55% of CGRP-positive neurons were 5-HT1D immunoreactive. Approximately 50% of CGRP-positive neurons were SP-positive, while 93% of SP-positive neurons were CGRP-positive, suggesting that nearly all SP-positive neurons also contain CGRP. The fibre types of the 5-HT1B- and 5-HT1D-positive neurons were further investigated with an antibody against the A-fibre marker 200-kDa neurofilaments (NF200). Approximately 46% of the 5-HT1B-positive and 43% of the 5-HT1D-positive trigeminal ganglion neurons were also NF200 positive, indicating that many A-fibre trigeminal neurons express 5-HT1B or 5-HT1D receptors. These results support the hypothesis that one important action of antimigraine drugs is the inhibition of CGRP release and that Adelta-fibres may play an important role in migraine pathogenesis.

Analysis of hard thoracic herniated discs: review of 18 cases operated by thoracoscopy

The authors retrospectively reviewed a series of 18 hard thoracic herniated discs (HTHD) operated by thoracoscopy. Isolated cases of HTHD have been reported in the literature, but no series describing these lesions has been published. Seventy-two percent of the herniated discs were situated between T8 and T12. Fifty-six percent of the patients had radiographic sequelae of Scheuermann's disease. Postoperatively, 83% had neurological improvement. In seven cases (39%), a plane separating the herniated disc and the dura mater was found surgically. In 11 patients, no separating plane was found during surgery. The lesion was intradural in three patients (17%) and adherent to the dura mater in eight (44%). Among these 11 patients, surgery was complicated by a dural tear in the first seven that led to a high risk of cerebrospinal fluid fistula: four of these seven patients had required surgical revision. In the last four, the zone of adhesion of the HTHD to the dura mater was preserved, successfully preventing dural tear.

Spinal dural arteriovenous fistula

PURPOSE OF REVIEW

To summarize clinical key points, diagnostic features, and results of imaging and therapy of spinal dural arteriovenous fistula (SDAVF).

RECENT FINDINGS

SDAVF accounts for 70% of spinal arteriovenous malformation with an annual incidence of 5-10 cases per million. At least 80% of patients are male, and more than 66% of patients are in the sixth and seventh decade of life indicating preponderance of gender and age. Thrombophilia is not a predisposing factor of disease. Clinical course is predominated by symptoms of congestive myelopathy, but subarachnoid hemorrhage may occur. Double SDAVF is a rare problem in the management of disease. Magnetic resonance imaging has replaced myelography as screening procedure. Contrast-enhanced magnetic resonance angiography and multislice computerized tomographic angiography may facilitate diagnostic procedure, however, spinal angiography is still required to confirm diagnosis. Treatment by permanent occlusion of fistula results in clinical improvement in 70% of cases. Microsurgical shunt interruption has proven secure and reliable. Endovascular shunt embolization has been established as a standardized procedure, but occlusion rates are still lower than in surgical treatment.

SUMMARY

Advances have been made in diagnosis and treatment of SDAVF, but the disease is still not completely understood.

Cauda equina syndrome secondary to idiopathic spinal epidural lipomatosis

STUDY DESIGN

Three cases of idiopathic epidural lipomatosis are reported.

OBJECTIVES

Description of the relationship between spinal pathologic overgrowth of fat tissue and neurologic symptoms.

SUMMARY OF BACKGROUND DATA

Idiopathic epidural lipomatosis is a very rare condition; it is usually secondary to chronic steroid therapy or endocrinopathic diseases.

METHODS

Three men with a mean age of 58.5 years, who experienced intermittent claudication, bilateral radicular pain in both legs, and urinary dysfunction with hypoesthesia in the perineal region, were evaluated by plain radiography and magnetic resonance imaging, the results of which demonstrated a pathologic overgrowth of fat tissue in the spinal canal with a marked impingement of the dural sac. Obesity, endocrinopathic diseases, and chronic steroid therapy were excluded for all patients. Surgical treatment was performed by wide multilevel laminectomies, fat debulking, and instrumented posterolateral fusion.

RESULTS

After surgery there was a gradual improvement in symptoms and signs so that 2 years later the patients returned to daily activities and were neurologically normal.

CONCLUSIONS

Spinal epidural lipomatosis can be a cause of back pain but rarely radicular impingement. Magnetic resonance imaging is the procedure of choice. The treatment must be performed early by wide surgical decompression.

Extradural Motor Cortex Stimulation (EMCS) for Parkinson’s disease. History and first results by the study group of the Italian neurosurgical society

The preliminary results obtained by the Study Group for Treatment of Involuntary Movements by Extradural Motor Cortex Stimulation (EMCS) of the Italian Neurosurgical Society, are reported. The series includes 16 cases of very advanced Parkinson's Disease (PD), aged 46-81; 15 of them were not eligible for Deep Brain Stimulation. Ten cases have been evaluated at 3-30 months after implantation. Unilateral, sub-threshold extradural motor cortex stimulation (2 8 Volt, 100-400 microsec., 20-120 Hz) by chronically implanted electrodes, relieves, at least partially, but sometime dramatically, the whole spectrum of symptoms of advanced PD. Tremor and rigor bilaterally in all limbs and akinesia are reduced. Standing, gait, motor performance, speech and swallowing are improved. Benefit is marked as far as axial symptoms is concerned. Also the symptoms of Long Term Dopa Syndrome -dyskinesias, motor fluctuations - and other secondary effect of levodopa administration psychiatric symptoms - are improved. Levodopa dosage may be reduced by 50%. The effect seems persistent and does not fade away with time. Improvement ranged, on the basis of the UPDRS scale, from <25% to 75%. There was only one case of complete failure. Quality of life is markedly improved in patients who were absolutely incapable of walking and unable arise out of chair. After stimulation they could walk, even if assistance was necessary. Improvement was observed also in those with disabling motor fluctuation and dyskinesias which could be abolished.

Referral of pain from dural stimulation in man

✓ Electrical stimulation of the dura was carried out in 25 patients using chronically implanted electrodes to determine areas of referred pain. Referred pain occurred over areas supplied by all divisions of the trigeminal nerve and the upper three cervical spinal nerves. No pattern of pain referral could be established on the basis of electrode positions determined from bone landmarks on the skull. It is suggested that these findings may be explained either by a greater overlap of the dural nerves than had been previously recognized, or by an overlap of the connections of the cervical nerves and the trigeminal nerve in the dorsal horn of the cervical spinal cord. Both of these mechanisms seem to be operative to some degree. Bilateral and contralateral pain was also elicited; whether this was due to stimulation of the bilateral termination of the dural nerves near the midline or of the bilateral central projections of these dural nerves is not clear. Contralateral referral of pain from dural points widely separated from the midline, however, suggests that some contralateral central projections do exist. The authors conclude that head pain of dural origin has limited clinical usefulness because of the lack of consistent specificity in its referral pattern.

Pressure changes within the cauda equina following constriction of the dural sac. An in vitro experimental study

In order to register pressure changes within the cauda equina, a highly sensitive pressure measuring catheter was inserted through a hole in the dural sac. Its tip was placed among the nerve roots of the cauda equina at levels L2, L3, and L4 in seven freshly removed human specimens. The cross-sectional area of the dural sac then was decreased gradually by constriction of a circular clamp. The inside diameter of the clamp and the corresponding area was determined when further reduction of the circumference of the clamp caused the first signs of a pressure increase, the critical size, among the nerve roots. The average critical size was 76.9 mm2 at the L2 level, corresponding to a diameter of 11.4 mm At the L3 level, the corresponding figures were 71.5 mm2 and 11.1 mm, and at the L4 level 64.8 mm2 and 10.6 mm, respectively. It seemed reasonable to assume that the critical sizes determined in this way could be threshold values below which a further constriction of the size of the dural sac would cause an impairment of the circulatory and/or the nerve function of the cauda equina.