Shear viscosity and nonlinear behavior of whole blood under large amplitude oscillatory shear.

We investigated experimentally the rheological behavior of whole human blood subjected to large amplitude oscillatory shear under strain control to assess its nonlinear viscoelastic response. In these rheological tests, the shear stress response presented higher harmonic contributions, revealing the nonlinear behavior of human blood that is associated with changes in its internal microstructure. For the rheological conditions investigated, intra-cycle strain-stiffening and intra-cycle shear-thinning behavior of the human blood samples were observed and quantified based on the Lissajous-Bowditch plots. The results demonstrated that the dissipative nature of whole blood is more intense than its elastic component. We also assessed the effect of adding EDTA anticoagulant on the shear viscosity of whole blood subjected to steady shear flow. We found that the use of anticoagulant in appropriate concentrations did not influence the shear viscosity and that blood samples without anticoagulant preserved their rheological characteristics approximately for up to 8 minutes before coagulation became significant.

Regional variations in brain oxygenation during temporary clipping in aneurysm surgery.

OBJECTIVES: Brain tissue oxygen concentration (PbtO(2)) monitoring has been used in aneurysm surgery to detect decreased brain oxygenation during temporary clipping. The effects of circulatory interruption according to different aneurysm locations have not been established. In this work, variations in PbtO(2) during temporary clipping were studied in anterior communicating (AcomA), posterior communicating (PcomA) origin, and middle cerebral artery (MCA) aneurysm surgery. METHODS: PbtO(2) was monitored during surgery of 41 patients; aneurysms were located in the AcomA (10 cases), origin of PcomA (8 cases), and MCA bifurcation (23 cases). Temporary clips were used in all cases. Variations in PbtO(2) values obtained during application of temporary clips were evaluated and studied according to the duration and type of circulatory interruption for each aneurysm location. RESULTS: In AcomA aneurysm surgery, a significant decrease in PbtO(2) values was found in 31% of the periods of temporary clipping, whereas in PcomA and MCA aneurysm surgery, significant decreases were found in all temporary clip applications (100%). In MCA aneurysms, the amplitude of decrease in PbtO(2) was higher when the circulatory interruption lasted for 2 or more minutes, compared with shorter periods of temporary clipping. DISCUSSION: During temporary clipping, different variations in PbtO(2) values were obtained when comparing frontal and temporal regions of monitoring: in MCA and PcomA origin aneurysms, significant variations were registered in all periods of temporary regional circulatory interruption, but the same results were not found in frontal monitoring for AcomA aneurysm surgery.

Intraoperative brain oxygenation monitoring and vasospasm in aneurysmal subarachnoid hemorrhage.

BACKGROUND: Vasospasm is a frequent complication of subarachnoid hemorrhage (SAH), implicated in poor outcome, and prediction of its occurrence might be important on the therapeutic approach of this condition. Brain oxygenation in aneurysmal SAH was prospectively monitored during surgery in 28 patients, using brain tissue oxygen pressure (PbtO(2)), studying its association with the occurrence of post-operative vasospasm, detected by transcranial Doppler. METHODS: PbtO(2) monitoring was performed during surgery of 28 patients with aneurysmal SAH, using a polarographic microcatheter (Licox; GMS, Kiel, Germany), inserted into the cerebral tissue. The aneurysms were localized in the anterior communicating artery (AcoA) complex (eight cases), in the posterior communicating artery (Pcom) origin (seven cases), and in the middle cerebral artery (MCA) bifurcation (13 cases). Basal PbtO(2) values, obtained immediately before application of temporary or definitive clips, were studied according to age, clinical status and CT findings. The association between the basal values and the occurrence of increased blood flow velocity in the post-operative transcranial Doppler (TCD vasospasm) was investigated. RESULTS: Post-operative TCD vasospasm developed in 13 patients, all of them with basal values inferior to 10 mmHg. PbtO(2) basal value was significantly lower in cases that developed TCD vasospasm. This association was independent of age, clinical status, or CT findings. CONCLUSION: The finding of low intraoperative basal PbtO(2) values may be an indicator for a high risk of occurrence of post-operative TCD vasospasm in cases of aneurysmatic SAH.

Monitoring of brain tissue oxygenation in surgery of middle cerebral artery incidental aneurysms.

INTRODUCTION: The management of incidental unruptured aneurysms remains a matter of controversy; middle-sized or large anterior circulation incidental aneurysms, in young or middle age patients, should be considered for treatment. Surgical clipping is an accepted treatment for middle cerebral artery unruptured aneurysms. Ischemic events can occur even in cases of incidental aneurysm surgery. Since regional cerebral blood flow can be compromised due to temporary arterial clipping or to incorrect placement of defi nitive clip, we performed intra-operative monitoring of brain tissue oxygen concentration (PtiO(2)), to detect changes in brain oxygenation due to reduced blood fl ow, eventually leading to ischemia, during surgery of middle cerebral artery incidental aneurysms. METHODS: PtiO(2) monitoring was performed during surgery of eight patients harboring incidental MCA aneurysms, using a polarographic microcatheter (Licox, GMS - Kiel, Germany), placed in the temporal lobe on the side of the lesion, from dural opening to dural closure. RESULTS: Basal values varied between 2.3 and 27.3 mmHg; these values are lower than those previously described in the literature as "normal" for uninjured brain or in cases of subarachnoid hemorrhage. In all patients, a significant decrease in PtiO2 was found in every period of temporary clipping of MCA. Post-operative infarction in the territory of middle cerebral artery occurred in one patient and, in that case, there was a persistent minimum value of 0.6 mmHg, without recovery after the placement of the definitive clip. In another patient, an incorrect placement of the definitive clip could be predicted by a decrease in PtiO(2) value. CONCLUSIONS: PtiO(2) monitoring during aneurysm surgery shows brain tissue perfusion in real time and there is a correlation between any episode of reduced blood flow to the affected vascular territory during surgery and a decrease of PtiO2 values. Unexpected low basal values were obtained in "uninjured" brain, with no influence from subarachnoid hemorrhage. The values of risk for brain infarction during temporary arterial occlusion still need further studies, but an incomplete recovery or a persistent fall in PtiO(2) values after definitive clipping should be considered as an indication for verification of the position of the clip.

[Cavernous malformation of the pineal region. Case report and review of the literature]. / Malformación cavernosa de la región pineal. Caso clínico y revisión de la literatura.

Cavernous malformations rarely occur in the pineal region with only 21 reported to date. Although its diagnosis is not easy because of the extreme rareness of this condition, the presence of this lesion can be suspected based on its typical radiological findings. We report the case of a 57-year-old woman presented with desorientation, somnolence and diplopy. The CT-scan showed an acute hemorrhage in the pineal region and triventricular hydrocephalus. An MRI suggested a cavernous malformation. The patient was operated with total en-bloc removal of the lesion. We conclude that surgical exploration and total resection is the treatment of choice when the diagnosis of cavernous angioma is suspected of the basis of neuroimaging.

[Trigeminal neuralgia caused by contra lateral cerebellopontine angle tumor. A case report]. / Neuralgia del trigémino provocada por un tumor del ángulo ponto-cerebeloso contralateral. Caso clínico.

In most cases, trigeminal neuralgia is due to compression of the trigeminal nerve in the zone of entrance at the pons by vascular structures. About 1% of cases, have trigeminal neuralgia associated with the presence of ipsilateral lesion of cerebellar-pontine angle. Rarely, trigeminal neuralgia may be due to contralateral posterior fossa tumors. We present a case of a 37-year- old patient who presented with right trigeminal neuralgia and harboured a left acoustic neuroma of significant dimension. Facial pain completely disappeared after tumor removal.

[Craniopharyngiomas. Clinicopathological aspects in different age groups]. / Craniofaringeomas. Aspectos clinicopatológicos em diferentes grupos etáirios.

Craniopharyngiomas are rare brain tumors of the hypothalamo-pituitary region, developing from embryonic remnants of Rathke's pouch and sac. Their overall incidence is 0.13 per 100,000 person years. Most frequently, they are suprasellar, start growing in childhood and originate neurological and hormonal symptoms. We retrospectively studied patients treated in our institution for craniopharyngioma in the last 10 years, in order to evaluate their clinical, imaging and pathological characteristics. Of the 32 patients analysed, 18 were females and 14 males with ages ranging between 6 and 81 years (early onset group--EOG aged 5-14 years: 7 patients; middle age onset group--MAOG aged 15-49 years: 15 patients; late age onset group--LOG aged > or = 50 years: 10 patients). Visual impairment was the most frequent presenting clinical feature in EOG (71.4%) and MAOG (86.6%), while in the LOG personality and cognitive changes including memory loss predominated (60%). Headaches were very frequent in all groups (EOG 42.8%, MAOG 60%, LOG 40%). Meningitis and seizures were presenting features, each in one patient. Regarding endocrine symptoms and signs, growth failure was present in 57.2% of the EOG. Amenorrhea was present in 5 of 10 female patients of the MAOG. Preoperatively, TSH was deficient in 25%, ACTH in 15.6% and gonadotropin in 25% of the patients. There were no cases of diabetes insipidus. Preoperative CT and MR revealed a calcified mass in 12 (37.5%), a partially cystic mass in 20 (62.5%) and a lesion involving or extending into the third ventricle in 7 (21.9%) patients. Twenty seven (84.4%) patients were treated primarily by surgery. In 4 (12.5%) cases the tumour was considered inoperable and 1 (3.1%) patient refused surgery; all were in the LOG. Surgical approach was transsphenoidal in 2/27 (7.4%) (all of them in the LAOG) and by craniotomy in the others. The tumour removable was considered complete in 10 (37%--EOG 2/7, MAOG 6/15, LOG 2/5) and subtotal in 17 (62.9%) patients. Eight (29.6%) patients were reoperated for recurrent tumour. Postoperative radiotherapy was administered in 12 cases with residual tumor, and 3 inoperable tumors were treated primarily by conventional external radiotherapy. Pathological study revealed the adamantinomatous type in 25 (92.6%) and the papillary type in 2 (7.4%--all men in the MAOG) tumors. The average follow-up was longer in the EOG (82.6 +/- 40.7 months) than in MAOG (57.2 +/- 48.5 months) and in LOG (48 +/- 92 months). Four (12.5%) patients died, 1 during the follow-up period due to a radiation-induced astrocytoma and 3 in the postoperative period because of cerebral hemorrhage and hydrocephalus (1 in the EOG and 2 in the LOG). In summary, we found the clinical presentation to be different in the 3 age groups, with a large number of patients in the MAOG. In this group were the only examples of the papillary form. Better prognosis was associated with a total resection at initial surgery.

[Reconstruction of the anterior cranial base with a frontal muscle flap in cerebrospinal fluid fistulae]. / Reconstrução da base anterior do crânio com o retalho de músculo frontal nas fístulas de líquido cefaloraquidiano.

Craniofacial infection is a major problem for the plastic and neurosurgical team. Previous successful experiences with free muscle and omentum flaps and the galea frontalis myofascial flap have been reported, avoiding disastrous complications after frontofacial advancements and the resection of skull base tumors. The authors report the clinical use of the galea frontalis myofascial flap in the treatment of anterior fossa CSF leaks. This flap provides an adequate sized and vascularized barrier between the cranial and nasal cavities through which the cells of the inflammatory response reach the target area. This technique was used in 11 cases with complete success; in-6 patients, repair of the anterior cranial base bone defect was performed with split calvarium bone grafts, harvested from craniotomy bone. In all the patients, neither the recurrence of the CSF leakage nor post-operative meningitis or its recurrence were observed.

The galea frontalis myofascial flap in anterior fossa CSF leaks.

We report the clinical use of galea frontalis myofascial flaps in the treatment of anterior fossa cerebrospinal fluid leaks after trauma. This flap provides an adequately sized and vascularised barrier between the cranial and nasal cavities through which the cells of the inflammatory response reach the target area. This technique was used in 9 cases with complete success; in 5 out of 9 patients, repair of an anterior cranial base bone defect was also performed with split calvarial bone grafts, harvested from the frontal craniotomy bone. In all patients, neither recurrence of the CSF leakage nor postoperative meningitis or its recurrence were observed.

HM-PAO spect in head trauma.

Single Photon Emission Computed Tomography (SPECT) after intravenous administration of Technetium-99m hexamethylpropylene-amine oxime (Tc-99m HM-PAO) makes possible the evaluation of cerebral perfusion. We have been assessing the diagnostic accuracy of SPECT in some groups of head trauma patients: the preliminary results of this study are presented. Fourteen patients have been selected, all of them showing some kind of focal neurological deficit; the Computed Tomography (CT) and Nuclear Magnetic Resonance (NMR) were normal, or showed lesions that could not be responsible for the neurological deficits. In all of the patients Tc-99m HM-PAO SPECT has been performed, showing changes in cerebral perfusion in areas correlated with the abnormalities elicited on clinical examination. These results show that Tc-99m HM-PAO SPECT is a better technique than CT or NMR in demonstrating the organic basis of some neurological deficits observed after head trauma.

Traumatic interhemispheric subdural haematomas.

According to reports in the literature traumatic interhemispheric subdural haematomas (I.S.H.) are supposed to present acutely or subacutely with contralateral monoparesis of a lower extremity or hemiparesis or in bilateral haematomas even with paraparesis, and to need early operative evacuation. In our series of 5 cases none of them followed this "classical" clinical picture, and three of them recovered without operation. We conclude that the indication for operative evacuation depends on the clinical course and that in patients with spontaneously improving symptomatology non-surgical management under close supervision may be the better solution. Also the C.T. finding of open convexity cisterns may be possible indication for conservative management.

Spinal cord hemangioblastoma with subarachnoid hemorrhage.

A case of subarachnoid hemorrhage caused by a cervical hemangioblastoma is presented. The clinical picture was indistinguishable from that of a subarachnoid hemorrhage from an intracranial lesion. The diagnosis was established by angiography and water-soluble contrast myelography followed by cervical computed tomographic scan. At surgery, the tumor was completely removed, and no neurological deficit was observed after the operation.