To reverse or not to reverse? A systematic review of autograft polarity on functional outcomes following peripheral nerve repair surgery.

BACKGROUND: The literature describing the best clinical practice for proximal-distal autograft orientation, otherwise known as nerve graft polarity, is inconsistent. With existing disparities in the peripheral nerve literature, the clinical question remains whether reversing nerve autograft polarity bears an advantage for nerve regeneration. METHODS: A comprehensive review of the literature using Embase and PubMed databases (1940-June 2015) was performed to retrieve all original articles on the effects of nerve autograft polarity on nerve regeneration and functional recovery following primary repair of peripheral nerve defects. RESULTS: The initial database search yielded 318 titles. Duplicate exclusion, title review and full text review yielded six articles which directly compared nerve autograft polarity. Histological, morphometric, electrophysiological, and behavioral outcomes were reviewed. All retained articles were animal studies, of which none demonstrated significant differences in outcomes between the normal and reversed polarity groups. A reversed graft may ensure that regenerating nerve fibers are not lost at branching points, however this may not translate into improved function. CONCLUSION: There is insufficient data to suggest that nerve autograft polarity has an impact on nerve regeneration and functional outcomes.

Physiologic Effects of Xenon in Xenon-CT Cerebral Blood Flow Studies on Comatose Patients.

Despite more than 30 years of clinical use, questions remain about the safety of xenon gas in Xenon-CT cerebral blood flow (XeCTCBF) studies. In particular, xenon's effect on brain oxygen (PbtO2) in comatose patients is not well defined. Our objective was to assess the effect of a 4.5-min inhalation of 28 % stable xenon on several physiologic variables, including intracranial pressure (ICP), cerebral perfusion pressure (CPP), and PbtO2 in comatose patients (Glasgow Coma Scale [GCS] ≤ 8). Thirty-seven comatose patients who underwent 73 XeCTCBF studies were identified retrospectively from a prospective observational database. Changes in MAP, HR, SaO2, EtCO2, ICP, CPP, and PbtO2 measured at the start of xenon administration and every minute for 5 min thereafter were assessed. The maximum change in each variable also was determined for each scan to tabulate clinically relevant changes. Statistically, but not clinically significant changes in MAP, HR, and EtCO2 were seen. Xenon had no effect on ICP, and a small, but clinically insignificant decrease in CPP and PbtO2, was observed. There was a varied response to xenon in most measured variables. Clinically significant changes in each were infrequent, and readily reversed with the cessation of the gas. We conclude that xenon does not appear to have a clinically significant effect on ICP, CPP, and PbtO2 and so appears safe to evaluate cerebral blood flow in comatose patients.

Arteriovenous shunt visualization in arteriovenous malformations with arterial spin-labeling MR imaging.

BACKGROUND AND PURPOSE: A reliable quantitative technique for measuring arteriovenous (AV) shunt in vascular malformations is not currently available. Here, we evaluated the hypothesis that continuous arterial spin-labeled (CASL) perfusion MR imaging can be used to detect and measure AV shunt in patients with arteriovenous malformations (AVMs). MATERIALS AND METHODS: CASL perfusion MR imaging was performed in 7 patients with AVMs. Semiquantitative AV shunt estimates were generated based on a thresholding strategy by using signal-intensity difference (DeltaM) images to avoid potential errors in cerebral blood flow (CBF) calculation related to abnormal transit times and nonphysiologic blood-tissue water exchange in and around the AVMs. The potential for measuring CBF in regions distant from and near the AVM was explored, as was the relationship of CBF changes related to the size of the shunt. RESULTS: In all 7 cases, striking increased intensity was seen on CASL perfusion DeltaM maps in the nidus and venous structures draining the AVM. Shunt estimates ranged from 30% to 0.6%. Mean CBF measurements in structures near the AVMs were not significantly different from the contralateral measurements. However, CBF in adjacent ipsilateral white matter increased relative to the contralateral side as the percent shunt increased (P = .02). Cortical gray matter CBF Delta (contralateral-ipsilateral) values demonstrated the same effect, but the correlation was weak and not significant. Thalamic CBF decreased ipsilaterally with increasing percent AV shunt (P = .01), indicating a possible steal effect. Basal ganglia Delta values showed little change in CBF with the size of the AV shunt. CONCLUSION: CASL perfusion MR imaging can demonstrate AV shunting, providing high lesion conspicuity and a novel means for evaluating AVM physiology.

Structural MRI of carotid artery atherosclerotic lesion burden and characterization of hemispheric cerebral blood flow before and after carotid endarterectomy.

Collateral circulation plays a major role in maintaining cerebral blood flow (CBF) in patients with internal carotid artery (ICA) stenosis. CBF can remain normal despite severe ICA stenosis, making the benefit of carotid endarterectomy (CEA) or stenting difficult to assess. Before and after surgery, we assessed CBF supplied through the ipsilateral (stenotic) or contralateral ICA individually with a novel hemisphere-selective arterial spin-labeling (ASL) perfusion MR technique. We further explored the relationship between CBF and ICA obstruction ratio (OR) acquired with a multislice black-blood imaging sequence. For patients with unilateral ICA stenosis (n = 19), conventional bilateral labeling did not reveal interhemispheric differences. With unilateral labeling, CBF in the middle cerebral artery (MCA) territory on the surgical side from the ipsilateral supply (53.7 +/- 3.3 ml/100 g/min) was lower than CBF in the contralateral MCA territory from the contralateral supply (58.5 +/- 2.7 ml/100 g/min), although not statistically significant (p = 0.09). The ipsilateral MCA territory received significant (p = 0.02) contralateral supply (7.0 +/- 2.7 ml/100 g/min), while ipsilateral supply to the contralateral side was not reciprocated. After surgery (n = 11), ipsilateral supply to the MCA territory increased from 57.3 +/- 5.7 to 67.3 +/- 5.4 ml/100 g/min (p = 0.03), and contralateral supply to the ipsilateral MCA territory decreased. The best predictor of increased CBF on the side of surgery was normalized presurgical ipsilateral supply (r(2) = 0.62, p = 0.004). OR was less predictive of change, although the change in normalized contralateral supply was negatively correlated with OR(excess) (=OR(ipsilateral) - OR(contralateral)) (r(2) = 0.58, p = 0.006). The results demonstrate the effect of carotid artery stenosis on blood supply to the cerebral hemispheres, as well as the relative role of collateral pathways before surgery and redistribution of blood flow through these pathways after surgery. Unilateral ASL may better predict hemodynamic surgical outcome (measured by improved perfusion) than ICA OR.

Topic review: surface modifications enhancing biological activity of guglielmi detachable coils in treating intracranial aneurysms.

BACKGROUND: Endovascular therapy with Guglielmi detachable coils is an accepted treatment option for patients with intracranial aneurysms. However, an emerging technology in the realm of endovascular tools is the use of traditional Guglielmi detachable coils with biologically active substances complexed to the coil surface to enhance aneurysm occlusion. METHODS: We review the literature and current trends in modified Guglielmi detachable coils. Surface modifications with extracellular matrix proteins, growth factors, ion impregnation, and genetically altered cells have been used in animal studies to improve the cellular response of Guglielmi detachable coils. Similarly, coronary artery stents have been modified in several different ways to maintain vessel patency, contrary to the goal of endovascular therapy. We comparatively reviewed this literature to add insight into the evolution of the research on modified Guglielmi detachable coils. CONCLUSIONS: Guglielmi detachable coil modifications have the potential to enhance aneurysm obliteration with directed cellular responses. This may allow aneurysm occlusion with coils in less time than untreated coils, thus decreasing the risks of aneurysm enlargement and hemorrhage.

Incidence and clinical significance of frontal sinus or orbital entry during pterional (frontotemporal) craniotomy.

BACKGROUND AND PURPOSE: Frontal sinus entry, orbital entry, or both may occur during pterional craniotomy for microsurgical clipping of aneurysms. We sought to determine the incidence and clinical significance of these findings on postoperative CT scans. METHODS: Eighty-two postoperative CT scans of the head obtained from 81 patients (64 women, 17 men; age range, 25-80 years) were retrospectively reviewed over a 1-year period. These scans were reviewed independently by two blinded neuroradiologists for the presence and degree of orbit and frontal sinus entry that may have occurred during craniotomy. Clinical charts, operative notes, and discussions with the patients' neurosurgeons were reviewed to determine the clinical management and significance of these findings. RESULTS: Of the total 82 craniotomies reviewed, 77 (94%) had been performed via the pterional approach (43 right, 34 left). Twenty-three (30%) of these 77 studies revealed some evidence of penetration into the orbit or frontal sinus (orbit=65.2% [15/23]; frontal sinus=30.4% [7/23]; both=4.4% [1/23]). Only five of 16 patients with radiographic orbital penetration had evidence of involvement of intraorbital contents (ie, thickened lateral rectus, fat herniation, intraorbital air). Chart review revealed no complication or change in management. Of the seven patients with frontal sinus entry, three had mucosal exenteration and packing with antibiotic-coated gelfoam. No delayed complications (ie, persistent fever, mucocele, cerebrospinal fluid leak, air leak, or meningitis) were identified (follow-up period, 18-29 months). CONCLUSION: Frontal sinus or orbital entry is not uncommon after pterional craniotomy, but the incidence of immediate complications is rare.

Surgical treatment of common entrapment neuropathies in the upper limbs.

Entrapment neuropathies of the upper extremity are common, debilitating conditions. Most patients with these neuropathies are readily diagnosed on purely clinical grounds and may be effectively managed with nonoperative measures. However, the broad differential diagnosis often necessitates electrodiagnostic testing and radiographic imaging to clarify the situation. This review focuses on three of the most common entrapment neuropathies in the upper limbs: carpal tunnel syndrome (median nerve entrapment at the wrist), cubital tunnel syndrome (ulnar nerve entrapment at the elbow), and radial tunnel syndrome (posterior interosseous nerve entrapment). Anatomical considerations, patient evaluation, indications for surgical intervention, options for surgical approaches, outcomes, and complications are discussed.

Endovascular thrombolysis for symptomatic cerebral venous thrombosis.

OBJECT: The authors sought to treat potentially catastrophic intracranial dural and deep cerebral venous thrombosis by using a multimodality endovascular approach. METHODS: Six patients aged 14 to 75 years presented with progressive symptoms of thrombotic intracranial venous occlusion. Five presented with neurological deficits, and one patient had a progressive and intractable headache. All six had known risk factors for venous thrombosis: inflammatory bowel disease (two patients), nephrotic syndrome (one), cancer (one), use of oral contraceptive pills (one), and puerperium (one). Four had combined dural and deep venous thrombosis, whereas clot formation was limited to the dural venous sinuses in two patients. All patients underwent diagnostic cerebral arteriograms followed by transvenous catheterization and selective sinus and deep venous microcatheterization. Urokinase was delivered at the proximal aspect of the thrombus in dosages of 200,000 to 1,000,000 IU. In two patients with thrombus refractory to pharmacological thrombolytic treatment, mechanical wire microsnare maceration of the thrombus resulted in sinus patency. Radiological studies obtained 24 hours after thrombolysis reconfirmed sinus/vein patency in all patients. All patients' symptoms and neurological deficits improved, and no procedural complications ensued. Follow-up periods ranged from 12 to 35 months, and all six patients remain free of any symptomatic venous reocclusion. Factors including patients' age, preexisting medical conditions, and duration of symptoms had no statistical bearing on the outcome. CONCLUSIONS: Patients with both dural and deep cerebral venous thrombosis often have a variable clinical course and an unpredictable neurological outcome. With recent improvements in interventional techniques, endovascular therapy is warranted in symptomatic patients early in the disease course, prior to morbid and potentially fatal neurological deterioration.

The effectiveness of rapidly infused intravenous fluids for inducing moderate hypothermia in neurosurgical patients.

UNLABELLED: Moderate hypothermia is often used for cerebral protection during anesthesia for cerebral aneurysm clipping. No reliable, rapid, and practical noncardiopulmonary bypass methods for the induction of hypothermia to core temperatures <34 degrees C have been reported. We assessed the effects of IV administration of chilled 5% albumin (5 mL/kg at 1-6 degrees C) on core temperature after surface cooling to approximately 34 degrees C. We calculated thermal distribution volume from the change in core temperature after the chilled fluid infusions. We also compared rapid administration (5 mL/kg over 30 min) with very rapid administration (5 mL/kg over 3-5 min). Chilled albumin 5 mL/kg infused over 5 min reduced core temperature by 0.6+/-0.1 degrees C. The same volume of chilled albumin infused over 30 min reduced core temperature by 0.4+/-0.1 degrees C. The calculated thermal distribution volume was less than one third of total body volume. Because the thermal distribution volume in these hypothermic patients was much lower than total body volume, the chilled IV fluids in this study were 3 times more effective in inducing hypothermia than suggested by a simple calculation. To achieve maximal effectiveness, however, chilled fluids must be administered very rapidly (>100 mL/min) to avoid heat gains in standard IV tubing that occur even with rapid administration. IMPLICATIONS: Chilled IV fluids can be much more effective for the induction of hypothermia than commonly assumed, but they must be administered very rapidly to avoid heat gains in IV tubing.

Catamenial mononeuropathy and radiculopathy: a treatable neuropathic disorder.

OBJECT: The aim of this study was to investigate the indications and treatment options in patients with lower-extremity neuropathies and radiculopathies caused by endometriosis. METHODS: The authors identified five patients whose symptoms included catamenial pain, weakness, and sensory loss involving the sciatic and femoral nerves and multiple lumbosacral nerve roots. Radiographic studies supported the diagnosis of catamenial neuropathy or radiculopathy, but definitive diagnosis depended on surgical and pathological examination. Treatment of symptoms, including physical therapy and a course of antiinflammatory or analgesic medication, was not helpful. Patients responded favorably to hormonal therapy. Laparoscopy or open exploration for extrapelvic lesions was performed for diagnosis or for treatment when hormone therapy failed. Pain and sensory symptoms responded well to therapy. Weakness improved, but never recovered completely. CONCLUSIONS: Catamenial neuropathy or radiculopathy should be considered when evaluating reproductive-age women with recurring focal neuropathic leg pain, weakness, and sensory loss.

Hypertension, small size, and deep venous drainage are associated with risk of hemorrhagic presentation of cerebral arteriovenous malformations.

OBJECTIVE: To identify clinical and angiographic factors of cerebral arteriovenous malformations (AVMs) associated with hemorrhage to improve the estimation of the risks and help guide management in clinical decision making. METHODS: We conducted a retrospective analysis of 100 consecutive adults who have presented during the past 3 years to our institution with cerebral AVMs. Angiographic and clinical parameters were evaluated using multivariate logistic regression analysis to analyze factors associated with hemorrhagic presentation. RESULTS: The group had a mean age of 37.8 years; 53% were men, 48% presented with intracranial hemorrhage, and 40% presented with seizures. All 10 patients with cerebellar AVMs presented with hemorrhage. The following factors were independently associated with AVM hemorrhage: history of hypertension (P = 0.019; odds ratio [OR] = 5.36), nidal diameter <3 cm (P = 0.023: OR = 4.60), and deep venous drainage (P = 0.009: OR = 5.77). Dural arterial supply (P = 0.008; OR = 0.15) was independently associated with decreased risk of bleed. Location, nidal aneurysms, patient age, and smoking were not associated with increased or decreased bleeding risk. CONCLUSION: In this study, we found small AVM size and deep venous drainage to be positively associated with AVM hemorrhage. Dural supply was associated with a decreased likelihood of hemorrhagic presentation. Hypertension was found to be the only clinical factor positively associated with hemorrhage, a finding not previously reported. Smoking, although associated with increased risk of aneurysmal subarachnoid hemorrhage, was not associated with a higher risk of AVM hemorrhage.

Surgical treatment of intracranial aneurysms.

Intracranial aneurysms are dangerous lesions which may produce sudden death or neurological devastation in people who are often otherwise completely healthy. The definitive treatment for most of these lesions in microsurgical repair, and the cure rate is quite high. The indications for surgery include an accessible aneurysm in a patient who is healthy enough to tolerate general anesthesia and a major intracranial procedure. The timing of surgery following subarachnoid hemorrhage is still controversial, but early surgery is currently recommended for patients who are alert. Preoperative imaging studies are crucial in defining the precise anatomy of the aneurysm and any associated lesions and anomalies. Surgical approaches and techniques, anesthetic considerations, postoperative radiographic evaluation, overall results, and complications are discussed in this article.

Cigarette smoking-induced increase in the risk of symptomatic vasospasm after aneurysmal subarachnoid hemorrhage.

Vasospasm following aneurysmal subarachnoid hemorrhage (SAH) is correlated with the thickness of blood within the basal cisterns on the initial computerized tomography (CT) scan. To identify additional risk factors for symptomatic vasospasm, the authors performed a prospective analysis of 75 consecutively admitted patients who were treated for aneurysmal SAH. Five patients who died before treatment or were comatose postoperatively were excluded from the study. Of the remaining 70 patients, demographic (age, gender, and race) and clinical (hypertension, diabetes, coronary artery disease, smoking, alcohol abuse, illicit drug use, sentinel headache, Fisher grade, Hunt and Hess grade, World Federation of Neurological Surgeons grade, and ruptured aneurysm location) parameters were evaluated using multivariate logistic regression to determine factors independently associated with cerebral vasospasm. All patients were treated with hypervolemic therapy and administration of nimodipine as prophylaxis for vasospasm. Cerebral vasospasm was suspected in cases that exhibited (by elevation of transcranial Doppler velocities) neurological deterioration 3 to 14 days after SAH with no other explanation and was confirmed either by clinical improvement in response to induced hypertension or by cerebral angiography. The mean age of the patients was 50 years. Sixty-three percent of the patients were women, 74% were white, 64% were cigarette smokers, and 46% were hypertensive. Ten percent of the patients suffered from alcohol abuse, 19% from sentinel bleed, and 49% had a Fisher Grade 3 SAH. Twenty-nine percent of the patients developed symptomatic vasospasm. Multivariate analysis demonstrated that cigarette smoking (p = 0.033; odds ratio 4.7, 95% confidence interval [CI] 2.4-8.9) and Fisher Grade 3, that is, thick subarachnoid clot (p = 0.008; odds ratio 5.1, 95% CI 2-13.1), were independent predictors of symptomatic vasospasm. The authors make the novel observation that cigarette smoking increases the risk of symptomatic vasospasm after aneurysmal SAH, independent of Fisher grade.

Correlation of diffusion MRI and heat shock protein in a rat embolic stroke model.

The expression of 70 kDa heat shock protein (HSP-70) in focal ischemia occurs in regions that sustain sub-lethal ischemic injury, and may therefore be considered as a biological marker of the ischemic penumbra. In a rat embolic stroke model, using fibrin-rich emboli, we correlated the expression of HSP-70 mRNA with diffusion magnetic resonance imaging (MRI) to determine if HSP-70 mRNA expression was associated with alterations in the apparent diffusion coefficient (ADC) of brain tissue water, a putative early marker of cytotoxic injury that is readily measured in vivo. Serial ADC measurements were made for 120 min following embolic infarction in the right carotid artery territory. HSP-70 mRNA expression was observed at the boundaries of the densely ischemic zone, as judged by diffusion imaging. ADC values observed in HSP-70 mRNA-positive regions were intermediate between those observed in the ischemic core or in control regions. In addition, the volume of HSP-70 mRNA-positive tissue correlated positively with the volume of tissue showing intermediate ADC values at 120 min. These findings suggest that intermediate ADC values occur in penumbral regions. Heterogeneity of ischemic cellular injury is suggested as the basis for the intermediate ADC values observed in these regions.

Cerebral extraction of oxygen, lactate production, and perfusion pressure in gunshot wound to the head: case report.

A case of gunshot wound to the head is presented, in which the patient made a satisfactory recovery after a prolonged period of elevated intracranial pressure and increased cerebral extraction of oxygen. Even though cerebral extraction of oxygen was increased in the most acute phase, the arteriojugular lactate difference was never abnormally decreased (ischemic). This finding indicated that, in this patient, increased cerebral extraction of oxygen was not sufficient to result in global cerebral ischemia (increased cerebral lactate production). To our knowledge, this is the first report on frequent serial assessment of cerebral extraction of oxygen and lactate production in severe penetrating head injury.

Cavernous malformations of the third ventricle.

CAVERNOUS MALFORMATIONS ARE uncommon lesions that are usually present in the cerebral hemispheres. Less frequently, these malformations are seen in the brain stem, basal ganglia, or paraventricular regions. We report four cases of cavernous malformations of the third ventricle. Patients presented with symptoms of hydrocephalus, memory loss, and signs of hypothalamic dysfunction. Magnetic resonance imaging and computed tomography provided characteristic images of the three lesions preoperatively. All patients underwent direct surgical excision of the malformations. Two patients had a transcallosal, transventricular approach, the third underwent a transcortical, transventricular approach, and the fourth had an infratentorial supracerebellar approach. Postoperatively, the patient with hypothalamic dysfunction has not improved and underwent ventriculoperitoneal shunting. The second patient did well initially; however, 8 days postoperatively, she became comatose and later died. The presumed cause of her deterioration was a hypothalamic venous infarction. The third and fourth patients have returned to their normal neurological baseline. The presenting signs and symptoms, magnetic resonance imaging and computed tomography findings, and treatment options for this rare lesion are discussed and illustrated.

Lhermitte-Duclos disease and Cowden's syndrome in an adolescent patient. Case report.

Recent reports of seven cases of Lhermitte-Duclos disease occurring in adult patients with Cowden's syndrome (multiple hamartoma syndrome) strongly suggest that Lhermitte-Duclos disease is one of the types of neoplasia that characterize this syndrome. A case of Lhermitte-Duclos disease is reported in a 16-year-old girl with craniomegaly, choroidal hamartoma, and conjunctival papilloma of the right eye, and a history of bilateral multinodular adenomatous goiter and cystic hygroma. These findings strongly suggest a diagnosis of Cowden's syndrome. Although the syndrome traditionally has been defined by mucocutaneous criteria, it typically also involves hamartomas and neoplasia of internal organs, most commonly in the thyroid, breast, and female genitourinary tract. Because the mucocutaneous features may develop several decades after birth, the present case both supports the previously reported association between Lhermitte-Duclos disease and Cowden's syndrome and highlights the need for long-term follow-up monitoring of a pediatric patient with Lhermitte-Duclos disease because of the risk of malignancies associated with Cowden's syndrome.