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Biomedical subjects

E W Lang

Publications and source records attributed to E W Lang.

At least 19 recordsLinked to original sources
PubMed2001

Cerebral autoregulation testing after aneurysmal subarachnoid hemorrhage: the phase relationship between arterial blood pressure and cerebral blood flow velocity.

OBJECTIVE: Impairment of cerebral autoregulation (CA) appears to be an important cause for secondary ischemia after subarachnoid hemorrhage (SAH). It has been shown that graded CA impairment is predictive of outcome. Little is known about whether such impairment is present, what causes CA impairment, whether it precedes vasospasm, and whether it is predictive of outcome in patients with severe aneurysmal SAH. DESIGN: Prospective, controlled study. SETTING: Neurosurgical intensive care unit. PATIENTS: Twelve patients after aneurysmal subarachnoid hemorrhage, 40 controls. INTERVENTIONS: Recording of cerebral blood flow velocities and continuous measurement of arterial blood pressure at a controlled ventilatory frequency of six per minute to standardize the influence of intrathoracic pressure changes on blood pressure. MEASUREMENTS AND MAIN RESULTS: We calculated the phase shift angles (deltaphidegrees) between slow (0.1 Hz) arterial blood pressure and cerebral blood flow velocity waves measured by transcranial Doppler ultrasound in the middle cerebral artery during a) posthemorrhage days (PHD) 1-6 (early or prevasospasm phase), and b) during PHD 7-13 (late or vasospasm phase) using a 6/min ventilation protocol, and in 40 controls spontaneously ventilating at the same rate. deltaphi <30 degrees indicated lost CA. Mean flow velocities >100 cm/sec were considered vasospasm. We combined early and late measurements to assess the CA relationship with low cerebral perfusion pressure (CPP) and/or vasospasm. We assessed the Glasgow Outcome Scale (GOS) score at discharge (1 = worst, 5 = best). The admission Hunt and Hess score was 3.6 +/- 0.7. GOS scores were n = 3 (GOS 1), n = 2 (GOS 2), n = 5 (GOS 3), n = 1 (GOS 4), and n = 1 (GOS 5). In the early phase, deltaphi was 40.4 +/- 19.8 degrees (left), and 40.4 +/- 19.2 degrees (right). CPP was 69.4 +/- 10.9, intracranial pressure (ICP) was 6.7 +/- 2.8 mm Hg. In the late phase, deltaphi worsened in six patients and none improved: 32.1 +/- 21 degrees (left), and 26.9 +/- 17.2 degrees (right); CPP was 68.1 +/- 12.1, ICP was 7.5 +/- 3.7 mm Hg. CA was significantly impaired in both phases when compared with normal subjects (deltaphi: 65.7 +/- 24.5 degrees; p < .01 for early, p < .001 for late phase). In the early phase, seven of eight patients in whom autoregulation was intact had a GOS >2 at discharge and disturbed CA on at least one side was predictive of either vegetative condition at discharge or death (p < .01). In the late phase, deltaphi was no longer predictive of outcome. Spasm was present in 8 of 17 vessels (47%) in which CA was lost; no spasm was found in 25 of 28 vessels (89%) in which CA was intact (p < .01). A low CPP was present in 6 of 17 vessels (35%) in which CA was lost; a normal CPP was found in 21 of 27 vessels (78%) in which CA was intact (p > .05, NS). However, 14 of 17 vessels (82%) with lost CA showed spasm and/or low CPP while only 8 of 27 cases (30%) with intact CA had either spasm or low CPP (p < .001). CONCLUSIONS: CA can be assessed in a graded fashion in SAH patients. CA impairment precedes vasospasm; ongoing vasospasm worsens CA. CA assessment early after subarachnoid hemorrhage, within PHD 1-6, is predictive of outcome whereas late assessment is not. CA impairment is associated with cerebral vasospasm and low CPP.

Adult↗
PubMed2001

Stroke pattern interpretation: the variability of hypertensive versus amyloid angiopathy hemorrhage.

INTRODUCTION: It is commonly felt that cerebral amyloid angiopathy (CAA) related intracerebral hemorrhage (ICH) can be distinguished from hypertension (HTN)-related ICH by certain typical features on computerized tomography (CT) and magnetic resonance imaging (MRI). The purpose of this study was to investigate the performance of clinicians who were asked to differentiate between CAA and HTN based on hemorrhage pattern interpretation and to assess the feasibility of such classification. METHODS: The admission scans from 83 patients who were admitted to our service with an acute ICH were presented to 5 clinicians in a randomized and blinded fashion (1 junior, and 1 senior neurosurgical resident, 1 attending neurosurgeon, and 2 neurosurgeon-neuroradiologists). There were no patients who received oral anticoagulants other than low-dose aspirin, or who suffered from vascular malformations or tumors. Scans from 41 patients with a histologically proven diagnosis of CAA and from 42 patients with a clear history of HTN were investigated. Hematoma evacuation was done in all CAA patients and in 59% of HTN patients (n = 25). RESULTS: The overall average classification accuracy was 66.8% (range: 62.7-69.9). For correct HTN classification it was 69.5% (range: 64.3-81), and 63.9% for CAA, respectively (range: 48.9-75.6). There were negligible differences in classification accuracy among all observers. Patients with a CAA-related ICH were significantly older than patients with a HTN-related ICH (74 vs. 66.5 years, p < 0.05). There was a significantly higher number of hematomas >30 ml in CAA (85.3%) when compared with HTN (59.5%). No basal ganglionic hemorrhage was seen in CAA, but in 40.5% in HTN. Intraventricular hemorrhage was seen in 24.4% in CAA, and in 26.2% in HTN. Two patients (4.9%) with CAA, and 7 patients with HTN (16.7%) presented with cerebellar hematomas. CONCLUSIONS: Three of 10 scans were not correctly diagnosed regardless of the examiner's level of training. This calls into question the reliability of classifying the underlying pathological condition based on hemorrhage pattern interpretation on CT or MRI. The definite diagnosis of CAA- versus HTN-related hemorrhage requires a histopathological confirmation and should not be based solely on hemorrhage pattern interpretation.

Adult↗
PubMed2000

Giant cystic craniopharyngiomas with extension into the posterior fossa.

Between 1991 and 1998, 24 patients underwent surgery for a craniopharyngioma in our department. This group included two patients who had tumors with extensive growth along the midline, and along the posterior fossa in particular. In both cases suprasellar calcifications were typical features on magnetic resonance imaging (MRI) and computed tomography (CT). A 7-year-old boy presented with a 6-month history of headache, nausea, and progressive unilateral hearing loss. With a suboccipital approach it was possible to remove the main part of the tumor. In a 13-year-old boy headache and visual deterioration led to the diagnosis of a craniopharyngioma, which was removed with a pterional approach. For the neuroimaging work-up in such cases of atypically growing craniopharyngiomas MRI is the method of choice. Additional CT scanning is recommended, which provides valuable information about bony changes at the skull base due to space-occupying growth. CT substantiates the differential diagnosis if typical calcifications are seen.

Adolescent↗
PubMed2000

Spontaneous intracranial haematomas caused by neoplasms.

We report about 50 patients with spontaneous intracerebral haematomas (ICH) caused by intracranial neoplasms to assess the underlying histological condition, their presentation on admission, diagnostic work-up, treatment, histological diagnosis, and clinical outcome. These patients were identified in a prospective series of 2041 patients with intracranial neoplasms and 692 patients with spontaneous ICH, which were both consecutively collected over a nine-year-period. The frequency of ICH in patients with intracranial neoplasms was 2.4%. The frequency of tumour related ICH in the ICH group was 7.2%. The leading cause of tumour related ICH were metastases of extracranial origin (n = 18; 36%), followed by glioblastoma multiforme (n = 15; 30%). Nine patients (18%) had benign primary intracranial neoplasms. On admission 18 patients were somnolent (36%) and 14 patients (28%) were comatose. In 29 cases (58%) ICH was the first clinical sign of neoplastic disease, while in 21 patients (42%) a malignant tumour was already known. We operated on 45 patients (90%), four patients (8%) were not operated on because of poor clinical condition and died, one patient refused surgical treatment. Six patients (12%) died despite surgery. This series confirms the importance of a proper neuroradiological and clinical work-up of patients with suspected tumour related ICH followed by operative treatment and histological confirmation of the diagnosis. This is supported by the fact that 18% of patients had prognostically favourable intracranial tumours which would not otherwise have been adequately treated.

Acute Disease↗
PubMed2000

A bedside method for investigating the integrity and critical thresholds of cerebral pressure autoregulation in severe traumatic brain injury patients.

To avoid ischaemic secondary insults after severe head injury (SHI) it would be helpful to know the relationship between cerebral perfusion pressure (CPP) and intracranial pressure (ICP). Static cerebrovascular autoregulation (AR) was tested in 14 patients after SHI. Mean arterial pressure (MAP) was varied to detect changes in intracranial pressure (ICP) indicative of intact AR. Three types of responses were observed: (1) MAP elevation causes an increase in ICP; (2) MAP elevation has no or very little effect on ICP; (3) MAP elevation lowers ICP; Changes between types 1/2 and type 3 suggests AR breakpoints. Varying response types and breakpoints were observed between and within patients. Lower AR breakpoints were seen from 60 to 80 mmHg CPP, upper breakpoints were as high as 112. CPP monitoring achieves a twofold utility in targeted therapy: (1) defining the range of intact AR; and (2) lower AR breakpoint assessment to avoid secondary insults. Although the precise relationship between pAR breakpoints and the adequacy of cerebral perfusion to meet metabolic needs remains unclear, a technique such as described here is simple and has much to offer in targeting therapy toward specific pathophysiological processes in traumatic brain injury.

Adolescent↗
PubMed1999

A massive intrathecal cefazoline overdose.

This case report describes the clinical course of a patient who inadvertently received a massive intrathecal cefazoline overdose through a lumbar drain, which had been placed after trans-sphenoidal surgery for a pituitary adenoma. She received high-dose barbiturate therapy and was monitored with electroencephalography (EEG), somatosensory evoked potentials (SSEP), brainstem auditory evoked potentials (BAEP) and transcranial Doppler ultrasound (TCD). No cerebrospinal fluid (CSF) exchange was performed, but CSF was drained continuously with daily CSF-cefazoline level monitoring. Despite the extremely toxic dose, the patient soon recovered completely.

Adenoma↗
PubMed1999

Spontaneous oscillations of arterial blood pressure, cerebral and peripheral blood flow in healthy and comatose subjects.

Slow and rhythmic spontaneous oscillations of cerebral and peripheral blood flow occur within frequencies of 0.5-3 min-1 (0.008-0.05 Hz, B-waves) and 3-9 min-1 (0.05-0.15 Hz, M-waves). The generators and pathways of such oscillations are not fully understood. We compared the coefficient of variance (CoV), which serves as an indicator for the amplitude of oscillations and is calculated as the percent standard deviation of oscillations within a particular frequency band from the mean, to study the impairment of generators or pathways of such oscillations in normal subjects and comatose patients in a controlled fashion. With local ethic committee approval, data were collected from 19 healthy volunteers and nine comatose patients suffering from severe traumatic brain injury (n = 3), severe subarachnoid hemorrhage (n = 3), and intracerebral hemorrhage (n = 3). Cerebral blood flow velocities were measured by transcranial Doppler ultrasound (TCD), peripheral vasomotion by finger tip laser Doppler flowmetry (LDF), and ABP by either non-invasive continuous blood pressure recordings (Finapres method) in control subjects, or by direct radial artery recordings in comatose patients. Each recording session lasted approximately 20-30 min. Data were stored in the TCD device for offline analysis of CoV. For CoV in the cerebral B-wave frequency range there was no difference between coma patients and controls, however there was a highly significant reduction in the amplitude of peripheral B-wave LDF and ABP vasomotion (3.8 +/- 2.1 vs. 28.2 +/- 16.1 for LDF, p < 0.001; and 1.2 +/- 0.7 vs. 4.6 +/- 2.8 for ABP, p < 0.001). This observation was confirmed for spontaneous cerebral and peripheral oscillations in the M-wave frequency range. The CoV reduction in peripheral LDF and ABP oscillations suggest a severe impairment of the proposed sympathetic pathway in comatose patients. The preservation of central TCD oscillations argues in favor of different pathways and/or generators of cerebral and peripheral B- and M-waves.

Adult↗
PubMed1998

Unspecific long-term potentiation can evoke functional segregation in a model of area 17.

It has been shown recently in rat hippocampus that the synapse specificity of Hebbian long-term potentiation breaks down at short distances (< 100 microm). Using a neural network model we show that this unspecific component of long-term potentiation can be responsible for the robust formation and maintainance of cortical organization during activity-driven development. When the model is applied to the formation of orientation and ocular dominance in visual cortex, addition of an unspecific component to standard Hebbian learning, in combination with a tendency of left-eye and right-eye driven synapses to initially group together on the postsynaptic neuron, induces the simultaneous emergence and stabilization of ocular dominance and of segregated, oriented ON/OFF subfields. Since standard Hebbian learning cannot account for the simultaneous stabilization of both structures, unspecific LTP thus induces a qualitatively new behaviour. Since unspecific LTP only acts between synapses which are locally clustered in space, our results imply that details of the local grouping of synapses on the dendritic arbors of postsynaptic cells can considerably influence the formation of the cortical functional organization at the systems level.

Algorithms↗
PubMed1998

[Interhemispheric subdural hematoma].

The interhemispheric subdural hematoma (ISH) is a special subdural hematoma with regard to both location and symptomatology. The most widely described clinical signs and symptoms associated with an ISH are a lucid interval and the falx syndrome. The latter is featured by a contralateral hemiparesis that is accentuated in the lower extremity but spares the face. Minor head trauma or a preexisting coagulation disorder are also often found. Nonsurgical treatment should be chosen in patients with little neurologic dysfunction and a stable clinical course. Patients with progressive neurologic deterioration and focal neurologic deficits should be operated on without delay. This article provides a review of 99 published cases of ISH and adds 3 cases to the existing literature.

Cerebral Cortex↗
PubMed1998

A neural network model for the emergence of grating cells.

A correlation-based learning (CBL) neural network model is proposed, which simulates the emergence of grating cells as well as some of their response characteristics to periodic pattern stimuli. These cells, found in areas V1 and V2 of the visual cortex of monkeys, respond vigorously and exclusively to bar gratings of a preferred orientation and periodicity. Their non-linear behaviour differentiates grating cells from other orientation-selective cells, which show linear spatial frequency filtering.

Animals↗
PubMed1998

Simulations on the selectivity of 5-aminolaevulinic acid-induced fluorescence in vivo.

The knowledge of the exact time course of a photosensitizer in tumour and surrounding host tissue is fundamental for effective photodynamic therapy (PDT) and fluorescence-based diagnosis. In this study the time course of porphyrin fluorescence following topical application of 5-aminolaevulinic acid (ALA) using different formulations, concentrations and incubation times has been measured in amelanotic melanomas (A-Mel-3) (n = 54) grown in transparent dorsal skinfold chambers of Syrian golden hamsters and in human basal cell carcinomas (BCCs) (n = 40) in vivo. To simulate the accumulation of ALA-induced protoporphyrin IX (Pp IX), a three-compartment model has been developed and rate constants have been determined. The kinetics of both the A-Mel-3 tumours and the BCCs show a significantly higher fluorescence intensity in tumour as compared to normal surrounding host tissue. Maximal fluorescence intensity in A-Mel-3 tumours as a percentage of the reference standard used occurs 150 min post incubation (p.i.) using a 1, 3 or 10% (vol.) ALA solution buffered to pH 7.4 and 1 h incubation time. After a 4 h incubation time maximal fluorescence intensity in tumour is measured shortly p.i. A concentration of 10% ALA does not increase the fluorescence intensity as compared to 3% ALA following 4 h incubation, but either 3 or 10% ALA yields a significantly higher fluorescence after 4 h incubation time as compared to 1 h. The fluorescence intensity following an 8 h incubation reaches its maximum directly p.i. for all concentrations and then decreases exponentially. The fluorescence intensity in the surrounding host tissue shows no statistically significant difference regarding concentration or incubation time. At least during the first hour p.i., the fluorescence intensity measured in the surrounding tissue is lower as compared to that in the tumour in all groups. 24 h after topical application hardly any fluorescence is detectable in tumour or surrounding host tissue in all experimental groups. Incubating human BCCs with a 20% ALA cream (water-in-oil emulsion) or a 20% ALA gel (containing 40% dimethyl sulfoxide) for approximately 2 h yields a similar fluorescence intensity directly after incubation for either cream or gel. However, while yielding a maximum 120 min p.i. with cream, the fluorescence intensity increases for a longer time (about 2-3 h p.i.) and up to higher values using the gel formulation. In surrounding normal skin, cream as well as gel formulation yields a similar fluorescence intensity directly after incubation. Afterwards the fluorescence intensity decreases slowly using the cream whereas a further increase of the fluorescence intensity is measured in the normal skin with a maximum 240 min p.i. using the gel formulation. The results of the proposed three-compartment model indicate that the observed selectivity of accumulated porphyrins following topical application of ALA is mainly governed by an increased ALA penetration of the stratum corneum of the skin, an accelerated ALA uptake into the cell and a higher porphyrin formation in tumour as compared to normal skin tissue, but not by a reduced ferrocheletase activity.

Aminolevulinic Acid↗
PubMed1998

The utility of contrast-enhanced MR-angiography for posterior fossa giant cerebral aneurysm management.

The utility of magnetic resonance angiography is sometimes limited in the diagnostic workup of cerebral aneurysms with low flow and/or partial thrombosis when weighed against digital subtraction angiography. We present the case of a rare superior cerebellar artery giant, partially thrombosed aneurysm in which additional i.v. contrast-enhanced MRA sequences were comparable to digital subtraction angiography. It demonstrated not only the exact spatial resolution and correct anatomical relation but also the hemodynamics which were confirmed by intraoperative Doppler ultrasound. This report supports the feasibility and utility of i.v. contrast-enhanced MRA for posterior fossa giant cerebral aneurysm management.

Cerebellum↗
PubMed1997

Outcome after severe head injury: an analysis of prediction based upon comparison of neural network versus logistic regression analysis.

More reliable prediction of outcome would be helpful for clinicians who treat severely head-injured patients. To determine if neural network modeling would improve outcome prediction compared with standard logistic regression analysis and to determine if data available 24 h after severe head injury allows better prediction than data obtained within 6 h, we tested the ability of both techniques at these two times to predict outcome (dead versus alive) at 6 months. One thousand sixty-six consecutive patients with Glasgow Coma Scale scores of 8 or less during the first 24 h after injury were randomly divided into two groups. Data from the first group (n = 799) were used to develop the models; data from the second group (n = 267) were used to test the accuracy, sensitivity, and specificity of the models by comparing predicted and actual outcomes. The 6-month mortality rate was 63.5%. Our findings confirm the importance of age, Glasgow Coma Scale scores, and hypotension in predicting outcome. Using data available at 24 h improved the predictive power of both models compared with admission data; at both time points, however, the differences in the results obtained with the two models were negligible. We conclude that outcome (dead versus alive) at 6 months after severe head injury can be predicted with logistic regression or neural network models based on data available at 24 h. Critical therapeutic decisions, such as cessation of therapy, should be based on the patient's status 1 day after injury and only rarely on admission status alone.

Adolescent↗
PubMed1996

Myogenic motor-evoked potential monitoring using partial neuromuscular blockade in surgery of the spine.

STUDY DESIGN: The authors analyzed motor-evoked potentials using transcranial electrical cortical stimulation during spinal surgery in 40 patients under conditions of partial neuromuscular blockade. OBJECTIVES: The results were used to investigate the utility of motor-evoked potential monitoring to prevent neurologic injury in spinal surgery. SUMMARY OF BACKGROUND DATA: Noninvasive transcranial electrical motor-evoked potentials are reportedly effective in predicting postoperative spinal cord deficits caused by intraoperative occurrences. However, the sensitivity and specificity of these predictions have not been assessed under conditions of partial neuromuscular blockade during a wide variety of surgical procedures. METHODS: Compound muscle action potentials were recorded at the tibialis anterior muscle while general anesthesia was maintained with nitrous oxide, etomidate, and sufentanil. Surgery was performed at all spinal levels for a variety of diagnoses. RESULTS: Reference motor-evoked potential amplitudes, measured after induction of partial neuromuscular blockade, ranged from 25 to 7562 microV (median, 600 microV). Variation in intraoperative motor-evoked potential amplitude ranged from signal loss to a 3440% increase. A decrease to less than 20% of the individual reference value for motor-evoked potential amplitude occurred at least once in nine patients (22.5%) but as not associated with postoperative motor deficits. Two patients who had loss of motor-evoked potential signal without recovery did have postoperative motor deficits. Motor-evoked potentials predicted postoperative motor improvement in six patients. An improvement threshold of 160% of the reference amplitude predicted postoperative motor improvement with 100% sensitivity and 81% specificity. CONCLUSIONS: The authors support the utility of recording transcranial electrical motor-evoked potentials in spinal surgery under partial neuromuscular blockade. Recovery of lost motor-evoked potentials was not associated with postoperative motor deficits, whereas non-recovery of lost motor-evoked potentials was.

Adolescent↗
PubMed1996

Intervertebral disc space infection caused by Aspergillus fumigatus.

The authors describe the case of a 53-year-old woman who suffered from an Aspergillus fumigatus infection of the L2/3 intervertebral disc space unrelated to previous operations on her lumbar spine. After surgical debridement combined with amphotericin therapy she died on the 23rd postoperative day from a fulminant bacterial sepsis of pulmonary origin. Although she had intermittently used steroids for bronchial asthma, this is an unusual case of fungal infection of the lumbar spine in an apparently immunocompetent patient.

Amphotericin B↗
PubMed1996

Urinary retention and space-occupying lesions of the frontal cortex.

The authors present 2 cases in which urinary retention was related to supratentorial cortical lesions. These cases support the presence and function of a supratentorial center involved in control of the voiding reflex loop and indicate that lesions affecting this center can result in urinary retention rather than the syndrome of incontinence, urgency, and increased urinary frequency that is generally attributed to dysfunction of this system. In such cases, a clinical presentation of urinary retention in the absence of associated remarkable neurological deficits renders clinical evidence as a localizing sign.

Aged↗