Quantifying the contribution of ambient and indoor-generated fine particles to indoor air in residential environments.

UNLABELLED: Indoor fine particles (FPs) are a combination of ambient particles that have infiltrated indoors, and particles that have been generated indoors from activities such as cooking. The objective of this paper was to estimate the infiltration factor (Finf ) and the ambient/non-ambient components of indoor FPs. To do this, continuous measurements were collected indoors and outdoors for seven consecutive days in 50 non-smoking homes in Halifax, Nova Scotia in both summer and winter using DustTrak (TSI Inc) photometers. Additionally, indoor and outdoor gravimetric measurements were made for each 24-h period in each home, using Harvard impactors (HI). A computerized algorithm was developed to remove (censor) peaks due to indoor sources. The censored indoor/outdoor ratio was then used to estimate daily Finfs and to determine the ambient and non-ambient components of total indoor concentrations. Finf estimates in Halifax (daily summer median = 0.80; daily winter median = 0.55) were higher than have been reported in other parts of Canada. In both winter and summer, the majority of FP was of ambient origin (daily winter median = 59%; daily summer median = 84%). Predictors of the non-ambient component included various cooking variables, combustion sources, relative humidity, and factors influencing ventilation. This work highlights the fact that regional factors can influence the contribution of ambient particles to indoor residential concentrations. PRACTICAL IMPLICATIONS: Ambient and non-ambient particles have different risk management approaches, composition, and likely toxicity. Therefore, a better understanding of their contribution to the indoor environment is important to manage the health risks associated with fine particles (FPs) effectively. As well, a better understanding of the factors Finf can help improve exposure assessment and contribute to reduced exposure misclassification in epidemiologic studies.

Spondylolysis and isthmic spondylolisthesis: impact of vertebral hypoplasia on the use of the Meyerding classification.

BACKGROUND: Spondylolysis and isthmic spondylolisthesis are common multifactorial disorders. The extent of slipping of the spondylolytic vertebra is considered a major predicator for prognosis and further follow-up. Vertebral hypoplasia is a common finding associated with spondylolysis. The purpose of this study is to evaluate the incidence of hypoplastic vertebral bodies in patients with spondylolysis and in the general population and to analyse the impact of the findings on the measurement and grading of spondylolisthesis. METHODS: 140 patients with 141 levels of spondylolysis identified by MRI were included in this study. The slippage of the spondylolytic vertebral body and the size in the midline sagittal image were measured and correlated. In addition, a randomised control group was evaluated to test the hypothesis that shortened, hypoplastic vertebral bodies can also be found in the general population. RESULTS: Shortened, hypoplastic vertebrae were found in 50 patients with spondylolysis and none was found in the control group. These shortened vertebrae mimicked spondylolisthesis and in 19 patients the slippage equalled the shortening, thus mimicking spondylolisthesis, although only spondylolysis was present. CONCLUSION: Sagittal shortening of the spondylolytic vertebra is common and may mimic spondylolisthesis. In order to define and measure spondylolisthesis the shortening of the spondylolytic vertebra has to be taken into account.

Position dependent changes of the cerebral venous drainage--implications for the imaging of the cervical spine.

PURPOSE: This study demonstrates the physiological changes of the cerebral venous outflow routes in healthy humans in the recumbent and the sitting position employing positional MRI. METHODS: In five volunteers, the internal jugular veins and the cervical vertebral plexus were analyzed in the supine and sitting position using an open MR system. Axial T2-weighted scans and axial T1-weighted flow sensitive gradient echo sequences were acquired. The findings were compared to previously published anatomic descriptions from cadaver preparations. RESULTS: In the supine position, the internal jugular vein is the main route for the cerebral venous outflow. The mean area was 100 mm (2) (±29 mm (2)) for both sides together. In the sitting position, the jugular vein collapses (mean area: 11 mm (2)±2 mm (2)) and the vertebral venous plexus becomes more prominent. CONCLUSION: The position dependent changes in cerebral venous outflow can be imaged using positional MRI. The vertebral venous plexuses may mimic pathologies and physicians reading positional MRI images of the cervical spine should be aware of the physiological changes occurring in the erect position.

Nonconvulsive status epilepticus as a possible cause of coma in neurosurgical intensive care.

Nonconvulsive status epilepticus (NCSE) can occur in comatose patients without clinical signs of seizure activity. We evaluated the occurrence of NCSE in patients who were admitted to our neurosurgical intensive care unit between 1998 and 2000. EEGs were obtained from 158 patients with head trauma, spontaneous bleeding or brain tumour. Patients with clinically apparent seizure activity or no electrophysiological signs of seizure activity were excluded from the study. Epileptiform activity was seen in 28 out of 158 patients. 11/28 of these patients had a Glasgow-Coma-Scale (GCS) Score below 9 and showed continuous epileptiform discharge without clinical signs of seizure activity (NCSE). The clinical status of 4 of these 11 NCSE patients improved after initiation of anticonvulsive medication. NCSE may be an under-recognised cause of coma in neurosurgical intensive medicine. EEG should be included in the routine evaluation of comatose patients, even if clinical seizure activity is not apparent.

Spinal neurosurgery with the head-mounted "Varioscope" microscope.

We present a preliminary report on the intra-operative use of a head-mounted microscope ("Varioscope" Leica HM500) in spinal neurosurgery. The Varioscope is a dynamic microscope mounted on a head-set. It weights 297 g and measures 73 x 120 x 63 mm (length x width x height). It offers an infinitely variable range of magnification from 3.6x to 7.2x. The working distance ranges from 300 to 600 mm. The field of view varies between 30-144 mm, depending on the selected enlargement factor and the working distance. In addition to the zoom function, the device offers a focus function (automatic or on demand). The optical elements for focus and zoom are located in two separate tubes which are mounted on a middle section containing the mechanical components as well as the receiver unit for the focussing elements. The lenses are adjusted by means of motor-driven push/pull cables. The autofocus works well in larger operative fields and a working distance between 30 and 60 cm. Nevertheless, when used in today's "keyhole" approaches, the autofocus is not helpful when operating in deep structures. Based on the satisfactory results achieved in our series, we can recommend the Varioscope, especially when no stationary microscope is available. The portable device can be packed in a suitcase and can travel with the consultant microsurgeon to different hospitals and distant units. The built-in video camera is ideal for patients, staff, assistant surgeons, and student education with real-time video monitoring of procedures from the microsurgeon's perspective. For daily microsurgery, we felt more comfortable with fixed, stationary operating microscopes.

The hour-glass model of corpus callosum injury.

In this retrospective study, the authors analyze the frequency, anatomical distribution and the clinical outcome of 44 patients after severe head injury, with and without lesions of the corpus callosum (CC). 44 patients with severe head injury (GCS<9 on admission), who were admitted to the intensive care unit of the Department of Neurosurgery after trauma, underwent early MR-tomography (T1, T2 and FLAIR sequences) in addition to CCT performed on admission. CC lesions were found in about 1/3 of patients with severe head injury. Posterior (splenium) lesions of the CC were three times more common than anterior lesions. Patients with CC injury were much younger compared to patients without CC injury (25 versus 34 years). The Glasgow Outcome Scale (GOS) score after six months was poor (death, persistent vegetative state, severe disability, GOS>3) in all patients with CC injury when compared to patients without CC injury (GOS<4). CC lesions are an important parameter in the assessment of severe brain trauma, hinting at the mechanism of injury as well as the outcome of patients. If a patient does not awake after blunt head injury, MRT scans (including FLAIR sequences) are indicated. A CC lesion alone is not the cause of prolonged coma but indicates a severe diffuse injury resulting in functional deorganization of the brain. The mechanisms of CC injury are discussed and a new pathophysiological model, based on the hour-glass analogy, is presented.

Spondylolisthesis and posterior instability.

We present the case of a patient with a spondylolisthesis of L5 on S1 due to spondylolysis at the level L5/S1. The vertebral slip was fixed and no anterior instability was found. Using functional magnetic resonance imaging (MRI) in an upright MRI scanner, posterior instability at the level of the spondylolytic defect of L5 was demonstrated. A structure, probably the hypertrophic ligament flava, arising from the spondylolytic defect was displaced toward the L5 nerve root, and a bilateral contact of the displaced structure with the L5 nerve root was shown in extension of the spine. To our knowledge, this is the first case described of posterior instability in patients with spondylolisthesis. The clinical implications of posterior instability are unknown; however, it is thought that this disorder is common and that it can only be diagnosed using upright MRI.

Twenty-five years of auditory brainstem implants: perspectives.

The auditory brainstem implant (ABI) provides auditory sensations, recognition of environmental sounds and aid in spoken communication in more than 300 patients worldwide. It is no more a device under investigation but it is widely accepted for the treatment of patients who have lost hearing due to bilateral tumors of the vestibulocochlear nerve. Most of these patients are completely deaf when the implant is switched off. In contrast to the cochlear implants (CI), only few of the implanted patients achieve open-set speech recognition without the help of visual cues. In the last few years, patients with lesions other than tumors have also been implanted. Auditory perceptual performance in patients who are deaf due to trauma, cochlea aplasia or other non-tumor lesions of the cochlea or the vestibulocochlear nerve turned out to be much better than in NF2 tumor patients. Until recently, the target region for ABI implantation has been the ventral cochlear nucleus (CN). The electrodes are implanted via the translabyrinthine or retrosigmoid approach. Currently, new targets along the central auditory pathways and new, minimally invasive techniques for implantation are under investigation. These techniques may further improve auditory perceptual performance in ABI patients and provide hearing to a variety of types of central deafness.

Intrathecal opioids for intractable pain syndromes.

For more than 20 years intrathecal opioid application with implantable pumps is an option for selected patients with malignant as well as non-malignant pain. In general, most types of pain should be treatable by opioid medication. However, the associated systemic side-effects such as nausea, vomiting, constipation or the risk of suppression of the central nervous system hinder the application of oral or intravenous opioid therapy as a sole, widely applicable treatment. Causes of non-malignant pain that may represent an indication for intrathecal drug-delivery systems include: failed back syndrome, neuropathic pain, axial spinal pain, complex regional pain syndrome, diffuse pain, brachial plexitis, central pain, failed spinal cord stimulation (SCS) therapy, arachnoiditis, poststroke pain, spinal cord injury pain and peripheral neuropathy. Due to the proximity to the receptor sites, the therapeutic effect of intrathecal drug application lasts longer and the rate of systemic side effects is reduced. Before definitive pump implantation, the therapeutic effect of intrathecal opioid therapy is tested with an external pump. If there is no clear and satisfactory effect in this trial application, pump implantation is not indicated. In our patients, with a follow-up exceeding 3 years, the reduction of non-malignant pain (assessed with the Visual Analogue Scale, VAS) was good or excellent (pain decrease >50%) in 71.3% of the patients, fair (VAS 5-6) in 19.8% and poor (VAS 7-10) in 8.9%. After 3 years of continuous treatment, we observed catheter-related technical problems (catheter dislocation, obstruction, kinking, disconnection or rupture) in 17 of 165 patients. Pump malfunctions were very rare (8 of 165 cases) and limited to older pump types. Reversible, specific drug-related side effects of long-term therapy with intrathecal pumps developed in 32 of the 165 patients. In our series, the mean serum/cerebrospinal fluid (CSF) concentration ratio for morphine was 1/3000, which explains the low rate of systemic side effects. Local diffusion difficulties in CSF cause an uneven distribution of morphine in CSF. Therefore the clinical effect is markedly influenced by the position of the catheter tip, a fact that should be kept in mind during catheter implantation. Intrathecal drug application is cost effective and can significantly improve the quality of life in selected patients. An intensive training in this method and awareness of its specific complications is necessary for everyone to participate in the consulting and implanting team. Pumps for chronic intrathecal opioid application should only be implanted in specialized centers.

Neurosurgical pain therapy with epidural spinal cord stimulation (SCS).

Neurosurgical therapy for intractable pain with epidural implantable electrodes has become a widely used and efficient alternative when conservative or less invasive therapies are no longer effective. A complete interdisciplinary work-up is required before considering a patient as a candidate for a spinal cord stimulation (SCS) device. In more than 1300 patients we implanted an SCS device in our clinic; more than 52% reported a significant (>50%) long-term improvement for more than 3 years and a significant reduction in their analgesic drugs. Although placement of the electrode and implantation of the stimulator are technically easy to perform, they do carry a risk of potentially debilitating complications such as meningitis or component migration. Hence. SCS therapy should only be performed in specialized centers. In peripheral vascular disease (PVD) and angina, the initial results are very promising, but the long-term efficacy has to be proven by multicenter studies.

Intrathecal antispastic drug application with implantable pumps: results of a 10 year follow-up study.

Since 1986, more than 300 patients received an intrathecal baclofen (ITB) pump for the treatment of severe spasticity. Chronic ITB administration is a safe and effective method, which significantly decreases pathologically exaggerated muscle tone and improves the quality of life in most patients. This therapy is indicated in severe spasticity of cerebral or spinal origin that is unresponsive to oral antispastic medications. It is also useful in patients who may experience intolerable side effects when they receive orally effective baclofen doses. The therapeutic dose required to treat spasticity of cerebral origin is about three times higher than in spasticity of spinal origin. In carefully selected patients who suffer from spasticity, pump implantation is a cost-effective treatment which improves their quality of life. In our series with a follow-up period of 10 years, the ITB dose remained constant and no development of tolerance was observed in most patients. Destructive procedures such as myelotomy are no longer performed in our department in order to treat spasticity.

Neuroprosthetic hearing with auditory brainstem implants.

The auditory brainstem implant (ABI) does provide auditory sensations, recognition of environmental sounds and aid in spoken communication in about 300 patients worldwide. It is no more an investigative device but widely accepted for the treatment of patients who have lost hearing due to bilateral tumors of the hearing nerve who transmits the acoustic information from the cochlea to the brain. Most of the implanted patients are completely deaf when the implant is switched off. In contrast to cochlear implants, only few of the implanted patients achieve open-set speech recognition without the help of visual cues. On average, the ABI improves communicative functions like speech recognition at about 30% when compared to lip-reading only. The task for the next years is to improve the outcome of ABI further by developing new less invasive operative approaches as well as new hardware and software for the ABI device.

Visually evoked changes of blood flow velocity and pulsatility index in the posterior cerebral arteries: a transcranial Doppler study.

OBJECTIVE: Transcranial Doppler sonography (TCD) can detect visual evoked blood flow responses non-invasively and continuously with high temporal resolution. While the mean flow velocity response to visual stimuli is well documented, the response of the pulsatile characteristics of the waveform is less well known. METHOD: We examined the changes of blood flow velocity and pulsatility index (PI) in the posterior cerebral artery (PCA) in 50 healthy volunteers. TCD responses were measured in response to metabolic activation of the visual cortex by visual stimulation. RESULTS: A specific, stimulus-related increase of the mean flow velocity (MFV) in the PCA was found. The intensity of the blood flow response was significantly influenced by the complexity of the stimulus. During complex visual stimulation we found a mean flow velocity (MFV) increase of 29.4 % from the baseline in the subjects. However, a stimulus-related decrease was observed in the pulsatility index (PI); although the mean PI with closed eyes during baseline measurement was 1.18 (SD 0.27), on average, it fell significantly to 0.95 (SD 0.23) with the alternating chessboard and 0.82 (SD 0.22) during the complex stimulus condition. The relative decrement of the pulsatility index with increasing complexity of the visual stimulus is highly significant, with values of -19.5 % and -30.5 % compared to the baseline. CONCLUSION: These findings demonstrate the inverse correlation between MFV response and pulsatility index in the PCA. We assume that this decrease of the PI in the PCA may reflect the reduced regional vascular resistance in the visual cortex during visual stimulation.

Acute demyelination: diagnostic difficulties and the need for brain biopsy.

BACKGROUND: Despite the rapid development in neuro-imaging over the past two decades, ring like contrast-enhancing lesions on CCT or MRI still may pose a diagnostic challenge. The main differential diagnoses of these lesions include metastatic carcinoma, high-grade glioma and brain abscess. Acute demyelination seldom turns out to be the underlying pathology. METHOD: Retrospective analysis was done on six patients with acute demyelination treated at our neurosurgical department between 1990 and 2001. Clinical, radiological, PET, intra-operative and histological findings were evaluated. FINDINGS: In five patients, the diagnosis of acute demyelination was established by histopathological evaluation of stereotactic biopsy specimen, in the sixth patient following microsurgical extirpation of the lesion. Neuropathology revealed demyelination with the presence of myelin-phagocytosing macrophages. In addition, lymphocytic infiltrates were present. Symptoms and signs improved significantly after high-dose steroid therapy. CONCLUSIONS: Despite CNS tissue destruction, necrosis and cyst formation are not usually found in demyelinating disease, being rather more common in young patients with ring-like contrast-enhancing lesions on CCT and MRI. Though an incorrect diagnosis can lead to a potentially fatal therapeutic intervention, histological diagnosis should be made in all cases. Due to minimum morbidity, stereotactic biopsy is the method of choice to obtain representative specimens for histological diagnosis. Open microsurgery of these lesions is not indicated since conservative medical treatment with steroids results in a favourable outcome in most cases.

Rehabilitation of hearing and communication functions in patients with NF2.

Most patients with neurofibromatosis type 2 (NF2) lose hearing either spontaneously or after removal of their neurofibromas. The patient may benefit from conventional hearing aids if, due to modern microsurgery and intraoperative monitoring the integrity of the cochlea and the 8th nerve is preserved. With lost auditory function but preserved electrical stimulibility of the 8th nerve a cochlear implant may be appropriate. But if the patients have no remaining 8th nerve to stimulate, there is no benefit from cochlear implants. Until some years ago, vibrotactile aids, lip-reading, and sign language have been the only communication modes available to these patients. With auditory brain stem implants it is now possible to bypass both the cochlea and the 8th nerve and to stimulate the cochlear nucleus directly. Stimulation of the devices produces useful auditory sensations in almost all patients. Testing of perceptual performance indicated significant benefit from the device for communication purposes, including sound-only sentence recognition scores and the ability to converse on the telephone. Also lip-reading is significantly improved with brain stem implants. The successful work of an auditory brainstem program center depends very much on the close interdisciplinary collaboration between the Departments of Neurosurgery and ENT-surgery. In the future new developments like speech processing strategies and new designed electrodes accessing the complex tonotopic organization of the cochlear nucleus may further improve rehabilitation in these patients who would have been deaf some years ago.

Invasive cutaneous squamous cell carcinoma associated with actinic keratosis: a case with orbital invasion and meningeal infiltration.

BACKGROUND: It is suggested that most squamous cell carcinomas in sun-exposed areas arise from preexisting solar keratosis. Actinic keratosis is thought of as being a precursor to squamous cell carcinoma. This form of squamous cell carcinoma has been considered to be a relatively benign lesion. We report a case of invasive squamous cell carcinoma associated with actinic keratosis leading to orbit destruction and meningeal infiltration. OBJECTIVE: To demonstrate that well-differentiated tumors can act extremely aggressively with the potential toward infiltrative growth patterns. METHODS: Histologically controlled surgery along with multiple radiation therapy was performed. RESULTS: The tumor progressed inducing perineural invasion, orbit infiltration, osseous destruction, and meningeal invasion. CONCLUSION: The association of squamous cell carcinoma and actinic keratosis supports the concept of a causal relation. Excision with histologic examination of actinic keratosis seems to be useful for accurate diagnosis. Squamous cell carcinoma can represent an aggressive tumor with infiltrative growth pattern and should not be considered a benign lesion.

Operative treatment of tentorial herniation in herpes encephalitis.

Herpes simplex virus is the most common cause of acute viral encephalitis in children. Due to the variety of possible clinical manifestations the diagnosis is often overlooked in the early stages of the disease. Anti-viral therapy with acyclovir should be started whenever HSE is suspected. When there is further deterioration under virostatic therapy, a brain biopsy should be performed to verify the diagnosis. But even when the adequate medical therapy is established, massive brain edema and brain shift resulting in tentorial herniation can develop. Up to now the reported mortality of these patients is still around 30%. Here we report on a child with severe necrotizing herpes simplex encephalitis who developed severe tentorial herniation due to a right-sided mass lesion. The patient's status markedly improved after decompressive anterior temporal lobe resection. To our knowledge a similar case has not yet been reported in the literature. We suggest that anterior temporal lobe resection and decompressive craniotomy is of benefit in selected cases with tentorial herniation because both decompression and reduction of infectious material can be achieved.