Domenico d'Avella

Monitoring of brain tissue pressure with a fiberoptic device.

Continuous monitoring of brain tissue pressure can now be achieved with intracerebral placement of fiberoptic microtransducers. This study was undertaken to test the safety, accuracy, and reliability of this relatively new type of intracranial pressure (ICP) monitoring. Initially, the fiberoptic device was compared with a concurrently functioning intraventricular catheter in 18 patients. The results from the two methods corresponded closely over a wide range of pressures, and the correlation coefficient approached 1.0. Subsequently, this monitor was used for routine measurement of ICP in a series of almost 200 neurosurgical patients at risk of intracranial hypertension. The tracings showed good wave forms and consistent absolute values of ICP. No instances of hemorrhage, mechanical failure, or other complications were associated with this monitor, except one case of infection, which was not directly attributable to the device per se. When bilateral intraparenchymal pressures were recorded in patients with unilateral mass lesions, significant transitory pressure differentials between the ipsilateral and contralateral sides were documented. It is concluded that monitoring intraparenchymal pressure with the fiberoptic device offers safe and reliable ICP recordings for routine neurosurgical practice. In patients with unilateral masses, ICP should be measured in close proximity to the lesion.

Time-course of blood-brain barrier permeability changes after experimental subarachnoid haemorrhage.

Summary¶ An increase in blood-brain barrier (BBB) permeability after subarachnoid haemorrhage (SAH) has been described in humans and has been correlated with delayed cerebral ischemia and poor clinical outcome. Few studies examined in the laboratory the relationship between SAH and BBB, with contrasting results due to limitations in experimental probes adopted and in timing of observation. The aim of this study was to quantify the time-course of BBB changes after experimental SAH. Groups of eight rats received injections of 400 μl of autologous arterial blood into the cisterna magna. BBB was assessed 6, 12, 24, 36, 48, 60, and 72 hours after SAH and in sham-operated animals separately for cerebral cortex, i.e. frontal, temporal, parietal, occipital, subcortical gray matter (Caudate-Putamen-Thalamus), cerebellar cortex and nuclei, and brain stem by a spectrophotofluorimetric evaluation of Evans Blue dye extravasation. As compared to sham-operated controls, SAH determined a significant BBB permeability change beginning 36 hours after SAH, peaking at 48 hours, and normalizing on day 3. This study provides a quantitative description of the temporal progression and recovery of BBB dysfunction after SAH. These results have implications for the management of aneurysm patients and for assessing the rationale and the therapeutic window of new pharmacological approaches.

Microsurgical Anatomic Features of the Olfactory Nerve: Relevance to Olfaction Preservation in the Pterional Approach

OBJECTIVE: The pterional approach represents the standard approach for most lesions of the anterior and middle cranial fossa. It requires some degree of frontal lobe retraction, which may result in temporary or permanent damage of olfaction because of nerve avulsion or mechanical compression. The purpose of this study, based on microanatomic dissection of human cadaveric specimens, was to review the microsurgical anatomic features of the nerve and suggest operative nuances that may contribute to reducing the rate of postoperative olfactory dysfunction. METHODS: Twenty olfactory nerves and tracts were examined in 10 human cadaveric heads obtained from three fresh and seven formalin-fixed adult cadavers. A standard pterional craniotomy was performed. The olfactory nerve was dissected from its arachnoidal envelopes and then mobilized for an average length of 30 mm (range, 25–35 mm). RESULTS: The possible retraction of the frontal lobe was 10 to 15 mm. More retraction invariably resulted in nerve disruption. CONCLUSION: The standard sylvian and basal cistern opening may be insufficient to guarantee preservation of olfactory function. Early identification and arachnoidal dissection of the nerve may reduce the rate of olfaction compromise. The opening of the subarachnoidal space should be performed in a proximal-to-distal manner to allow early visualization of the olfactory bulb and its dissection. The arachnoidal dissection should be performed with sharp instruments, avoiding any traction on the posterior portion of the olfactory tract. Any direct retractor compression should also be avoided to spare the microvasculature lying on the dorsal surface of the nerve.

Does Lamina Terminalis Fenestration Reduce the Incidence of Chronic Hydrocephalus after Subarachnoid Hemorrhage

OBJECTIVE The incidence of chronic hydrocephalus requiring cerebrospinal fluid shunting was analyzed for a prospective series of 52 consecutive patients with ruptured cerebral aneurysms who underwent fenestration of the lamina terminalis during early microsurgical aneurysm repair. We hypothesized that, by creating an anterior ventriculocisternostomy, fenestration of the lamina terminalis would facilitate cerebrospinal fluid dynamics and decrease the risk of subsequent hydrocephalus. METHODS Patients were enrolled according to the following criteria: 1) age more than 40 years; 2) admission Hunt and Hess Grade 2 to 4; 3) initial subarachnoid hemorrhage severity of Fisher Grade 3 or 4; and 4) early microsurgical repair of an anterior circulation aneurysm. RESULTS The mortality rate in this series was 9.6%. Of the 47 surviving patients, 32 (68%) were discharged with a Glasgow Outcome Scale score of 5, 10 (21%) with a Glasgow Outcome Scale score of 4, and 5 (11%) with a Glasgow Outcome Scale score of 3. The follow-up period ranged from 12 to 60 months. Chronic hydrocephalus was radiographically and clinically evident in 3.8% of the total population. Shunt surgery was performed for two patients who exhibited symptoms resulting from hydrocephalus, corresponding to 4.2% of the surviving patients. CONCLUSION Estimates from the most recently published studies indicate that an incidence of chronic post-subarachnoid hemorrhage hydrocephalus (requiring shunt surgery) of 15 to 20% is representative for an average contemporary population of patients with aneurysmal subarachnoid hemorrhage. The lower incidence of chronic hydrocephalus observed in this series possibly reflects the favorable effect of lamina terminalis fenestration on cerebrospinal fluid dynamics.

Quantitative study of blood-brain barrier permeability changes after experimental whole-brain radiation

Basic mechanisms underlying the tolerance and reaction of the central nervous system to ionizing radiation are not known precisely. We investigated the possibility of a change in blood-brain barrier (BBB) function as a causative factor for early delayed whole-brain radiation-induced cerebral dysfunction. Rats were exposed to conventional fractionation (200 cGy/d, 5 d/wk; total dose, 4000 cGy). BBB changes were assessed by means of the quantitative 14C-alpha-aminoisobutyric acid technique and electron microscopy. Studies of the passage of horseradish peroxidase across the BBB permitted comparative quantitative isotopical and qualitative morphological data. Experiments were carried out 2 to 3 weeks after the completion of the radiation exposure. The transport of 14C-alpha-aminoisobutyric acid across the BBB increased significantly in cerebral cortex and cerebellar gray matter, averaging 1.3 to 1.5 times over the normal values. Electron microscopy disclosed an intense vesicular response of the cortical microvascular endothelium that occurred without the opening of the tight junctions and resulted in an intense transport of HRP across the intact endothelium. The present data indicate that moderate doses of whole-brain radiation induce well-defined changes in BBB function, which possibly are involved in the pathogenesis of radiation-induced cerebral dysfunction in humans.

Blood-Brain Barrier Permeability Changes after Experimental Subarachnoid Hemorrhage

Basic mechanisms underlying cerebrovascular permeability responses to subarachnoid hemorrhage (SAH) are still to be defined in detail. Previous investigations examining the occurrence of blood-brain barrier (BBB) breakdown after SAH in the experimental setting have yielded conflicting results. In a rat model of SAH, we assessed BBB changes by means of the quantitative [14C]-alpha-aminoisobutyric acid technique. Experiments were carried out on the second day post-SAH. In blood-injected rats [14C]-alpha-aminoisobutyric acid transport across the BBB increased significantly in cerebral cortices and cerebellar gray matter, averaging 1.3 to 1.5 times control values. The present data indicate that SAH induces well-defined changes in BBB function, possibly involved in the pathogenesis of post-SAH cerebral dysfunction in humans. Results reported here have also potential clinical implications for the management of aneurysm patients.

Regional changes in spinal cord glucose metabolism in a rat model of painful neuropathy

Spinal cord patterns of metabolic activity in a model of neuropathic pain were assessed in unanesthetized rats by the [14C]-2-deoxyglucose (2-DG) technique. Rats used in this procedure had demonstrable thermal hyperalgesia ipsilateral to sciatic nerve ligation and ipsilateral hindpaws that were lifted in a guarded position. The latter indicated possible spontaneous pain. Sciatic nerve ligation produced significant increases in glucose utilization in the dorsal and ventral horns of both sides, with greater activity present on the ipsilateral as compared to the contralateral side. Peak activity was in laminae V-VI, a region involved in nociceptive processing. Thus, a chronic increase in neuronal activity in these regions may reflect spontaneous neuropathic pain.

Microsurgical anatomic features of the lamina terminalis.

OBJECTIVE The lamina terminalis (LT) is a structure of considerable interest for microneurosurgery, and precise knowledge regarding its normal anatomic features and the variations thereof is required. The purpose of this study, which was based on microanatomic dissection of human cadaveric specimens, was to review the microsurgical anatomic features of the LT and its neurovascular relationships. The surgical implications of the morphometric data are discussed. METHODS The region of the LT was examined in 10 human cadaveric heads, obtained from 8 fresh adult cadavers and 2 formalin-fixed adult cadavers, and in 10 formalin-fixed, isolated, adult brains. An operating microscope was used for all dissections and measurements. RESULTS Assuming the LT to be a triangular structure, we performed measurements of the distance between the midportion of the upper edge of the chiasm and the lower edge of the anterior commissure (height), which averaged 8.25 mm. The distance between the medial edges of the optic tracts (base) averaged 12.81 mm. The area averaged 52.84 mm2. A minimal amount of retraction was needed to fully expose the LT, and generally there was no need to mobilize the anterior cerebral artery-anterior communicating artery complex. Perforating branches to the hypothalamus and optic apparatus are laterally located and do not interfere with LT incision and/or fenestration. CONCLUSION The LT constitutes a clearly identifiable microsurgical target. The allowable extent of LT opening is sufficient to provide wide access into and free cerebrospinal fluid flow from the third ventricle. Fenestration of the LT is a safe procedure, provided that the relevant anatomic landmarks are identified and respected.

Time-related ultrastructural changes in an experimental model of whole brain irradiation.

To stimulate therapeutic irradiation, we exposed rats to conventional fractionation (200 +/- 4 cGy/d, 5 d/wk; total dose, 4000 cGy). The effects of this regimen were assessed by electron microscopic examinations of brain microvascular and parenchymal cells 15 and 90 days after irradiation. Studies of the transendothelial passage of horseradish peroxidase provided information about the functional status of the blood-brain barrier. At 15 days after irradiation, there was an increased vesicular transport of horseradish peroxidase across the intact endothelium without opening of the tight junctions, and without evidence of structural alterations of neuropil, neuronal bodies, and astrocytes. Ninety days after irradiation, well-defined ultrastructural alterations were observed, involving the microvasculature, the neuropil, the neuronal bodies, and astrocytes. The main ultrastructural feature of cortical microvessels was their collapsed aspect, associated with perivascular edema containing cell debris. Altered neurons and reactive activated astrocytes were also noticeable. These data suggest a possible association, not necessarily causal, between damage of the microvascular/glial unit of tissue injury and development of radiation-induced brain toxicity.

Traumatic intracerebellar hemorrhage: Clinicoradiological analysis of 81 patients

OBJECTIVE We report 81 patients with a traumatic intracerebellar hemorrhagic contusion or hematoma managed between 1996 and 1998 at 13 Italian neurosurgical centers. METHODS Each center provided data about patients’ clinicoradiological findings, management, and outcomes, which were retrospectively reviewed. RESULTS A poor result occurred in 36 patients (44.4%). Forty-five patients (55.6%) had favorable results. For the purpose of data analysis, patients were divided into two groups according to their admission Glasgow Coma Scale (GCS) scores. In Group 1 (39/81 cases; GCS score, ≥8), the outcome was favorable in 95% of cases. In Group 2 (42/81 cases; GCS score, <8), the outcome was poor in 81% of cases. Twenty-seven patients underwent posterior fossa surgery. Factors correlating with outcome were GCS score, status of the basal cisterns and the fourth ventricle, associated supratentorial traumatic lesions, mechanism of injury, and intracerebellar clot size. Multivariate analysis showed significant independent prognostic effect only for GCS score (P = 0.000) and the concomitant presence of supratentorial lesions (P = 0.0035). CONCLUSION This study describes clinicoradiological findings and prognostic factors regarding traumatic cerebellar injury. A general consensus emerged from this analysis that a conservative approach can be considered a viable, safe treatment option for noncomatose patients with intracerebellar clots measuring less than or equal to 3 cm, except when associated with other extradural or subdural posterior fossa focal lesions. Also, a general consensus was reached that surgery should be recommended for all patients with clots larger than 3 cm. The pathogenesis, biomechanics, and optimal management criteria of these rare lesions are still unclear, and larger observational studies are necessary.