Douglas J. Quint

Sleep apnea in patients with transient ischemic attack and stroke A prospective study of 59 patients

Although sleep apnea (SA) appears to be a cardiovascular risk factor, little is known about its frequency in patients with transient ischemic attack (TIA) and stroke.We prospectively studied 59 subjects (26 women and 33 men; mean age, 62 years) with stroke (n = 36) or TIA (n = 23) with the use of a standard protocol that included assessment of snoring and daytime sleepiness (Epworth Sleepiness Score [ESS]), a validated SA score (Sleep Disorders Questionnaire [SDQ-SA]), and a severity of stroke score (Scandinavian Stroke Scale [SSS]). SA was considered clinically probable (P-SA) when habitual snoring was associated with an ESS of >10 or when SDQ-SA score was >or=to32 in women and >or=to36 in men. Polysomnography (PSG) was obtained in 36 subjects (group 1) a mean of 12 days after TIA or stroke. In 23 subjects (group 2), PSG was not available (n = 11), refused (n = 10), or inadequate (n = 2). Clinical and PSG data were compared with those obtained in 19 age- and gender-matched control subjects. Groups 1 and 2 were similar in mean age (61 versus 64 years), type of event (36% versus 44% TIA), reported habitual snoring (58% versus 52%), and P-SA (58% versus 50%). PSG showed SA (Apnea-Hypopnea Index [AHI], >or=to10) in 25 of 36 subjects (69%). The proportion of subjects with SA was similar in the TIA and stroke groups (69% versus 70%) and was well above the frequency found in our control group (15%). An AHI of >or=to20 and a minimal oxygen saturation of <85% were each found in 20 of 36 subjects (55%). Gender and age did not correlate with severity of SA. Subjects with habitual snoring, P-SA, or severe stroke (SSS of <30) had a significantly higher AHI (p < 0.05). The sensitivity of P-SA for SA was 64%, and the specificity was 67%. We conclude that SA has a high frequency in patients in the acute phase of TIA and stroke and SA cannot be predicted reliably on clinical grounds alone but is more likely in patients with habitual snoring, abnormal SDQ-SA, or severe stroke. NEUROLOGY 1996;47: 1167-1173

Stereotactic navigation for placement of pedicle screws in the thoracic spine

OBJECTIVEPedicle screw fixation in the lumbar spine has become the standard of care for various causes of spinal instability. However, because of the smaller size and more complex morphology of the thoracic pedicle, screw placement in the thoracic spine can be extremely challenging. In several published series, cortical violations have been reported in up to 50% of screws placed with standard fluoroscopic techniques. The goal of this study is to evaluate the accuracy of thoracic pedicle screw placement by use of image-guided techniques. METHODSDuring the past 4 years, 266 image-guided thoracic pedicle screws were placed in 65 patients at the University of Michigan Medical Center. Postoperative thin-cut computed tomographic scans were obtained in 52 of these patients who were available to enroll in the study. An impartial neuroradiologist evaluated 224 screws by use of a standardized grading scheme. All levels of the thoracic spine were included in the study. RESULTSChart review revealed no incidence of neurological, cardiovascular, or pulmonary injury. Of the 224 screws reviewed, there were 19 cortical violations (8.5%). Eleven (4.9%) were Grade II (≤2 mm), and eight (3.6%) were Grade III (>2 mm) violations. Only five screws (2.2%), however, were thought to exhibit unintentional, structurally significant violations. Statistical analysis revealed a significantly higher rate of cortical perforation in the midthoracic spine (T4–T8, 16.7%; T1–T4, 8.8%; and T9–T12, 5.6%). CONCLUSIONThe low rate of cortical perforations (8.5%) and structurally significant violations (2.2%) in this retrospective series compares favorably with previously published results that used anatomic landmarks and intraoperative fluoroscopy. This study provides further evidence that stereotactic placement of pedicle screws can be performed safely and effectively at all levels of the thoracic spine.

Sleep-Disordered Breathing in Patients With Acute Supra- and Infratentorial Strokes: A Prospective Study of 39 Patients

BACKGROUND AND PURPOSE Although recent studies suggest a high prevalence of obstructive sleep apnea (OSA) in patients with acute stroke, a systematic characterization of sleep-disordered breathing based on the severity and topography of stroke has not been performed. METHODS We prospectively studied 39 noncomatose adult subjects (15 women, 24 men; mean age, 57 years) with a first acute stroke. Sleep history, cardiovascular risk factors, stroke severity as estimated by the Scandinavian Stroke Scale, and extent of stroke demonstrated on a computed tomographic or magnetic resonance imaging scan of the brain were assessed. Polysomnography was performed a mean of 10 days (range, 1 to 49 days) after stroke onset. Monitoring of breathing during wakefulness, non-rapid eye movement sleep, and rapid eye movement sleep included measurements of nasal/oral airflow, respiratory effort, and oxygen saturation. RESULTS Breathing was abnormal during wakefulness in 7 (18%) subjects and during sleep in 26 (67%). Obstructive sleep apnea (apnea-hypopnea index > 10) was found in 14 subjects, Cheyne-Stokes-like breathing was observed in 4, and a combination of obstructive sleep apnea and Cheyne-Stokes-like breathing was observed in 7. Sustained tachypnea and ataxic breathing were rare. No significant differences were found in age, body mass index, history of snoring or hypersomnia, or stroke topography or severity between subjects with and without sleep-disordered breathing. Prevalence and severity of breathing disturbances were also similar between patients with supratentorial stroke (n = 28) and those with infratentorial (n = 11) stroke. CONCLUSIONS Sleep-disordered breathing is frequent in patients with acute stroke, rarely has localizing value, and can also be found in patients with mild neurological deficits. Respiratory disturbances in stroke victims can be explained only in part by topography and extension of acute brain damage.

Computerized tomographic localization of clinically-guided sacroiliac joint injections.

OBJECTIVE The goal of this study was to use computed tomographic (CT) scanning to localize clinically guided sacroiliac (SI) joint injections and identify other structures affected by this procedure. DESIGN A prospective, double-blind, correlational outcome study design was used. Injection of 39 SI joints with a mixture of bupivacaine (0.25%), methylprednisolone (40 mg), and iohexol (Omnipaque; 180 mg/dl) using a clinically guided technique, (i.e., no image guidance) was performed. Patients had CT scans obtained both immediately after needle placement and after contrast injection. Neither the patients nor their clinicians were aware of the CT findings at the time of injection. SETTING Academic multidisciplinary pain center. PATIENTS Patients with SI disease by clinical criteria. RESULTS Intra-articular injection was accomplished in 8 of 37 (22%) patients. Injected material was identified within 1 cm of the joint 68% of the time. Epidural (spinal canal) injected material was seen 24% of the time. CONCLUSIONS The low rate of intra-articular injection seen with this clinically-guided technique suggests restraint in its use for injection therapy. Some image guidance (e.g., fluoroscopy, CT) is probably necessary to reliably inject the SI joint. Perhaps in clinical settings, where image guidance is not readily available, a clinically-guided technique could initially be tried in patients at low risk for complications from such injections. This study also provides an anatomic explanation for the occasional weakness observed after SI joint injection.

CONSIDERATION OF DOSE LIMITS FOR ORGANS AT RISK OF THORACIC RADIOTHERAPY: ATLAS FOR LUNG, PROXIMAL BRONCHIAL TREE, ESOPHAGUS, SPINAL CORD, RIBS, AND BRACHIAL PLEXUS

PURPOSE To review the dose limits and standardize the three-dimenional (3D) radiographic definition for the organs at risk (OARs) for thoracic radiotherapy (RT), including the lung, proximal bronchial tree, esophagus, spinal cord, ribs, and brachial plexus. METHODS AND MATERIALS The present study was performed by representatives from the Radiation Therapy Oncology Group, European Organization for Research and Treatment of Cancer, and Soutwestern Oncology Group lung cancer committees. The dosimetric constraints of major multicenter trials of 3D-conformal RT and stereotactic body RT were reviewed and the challenges of 3D delineation of these OARs described. Using knowledge of the human anatomy and 3D radiographic correlation, draft atlases were generated by a radiation oncologist, medical physicist, dosimetrist, and radiologist from the United States and reviewed by a radiation oncologist and medical physicist from Europe. The atlases were then critically reviewed, discussed, and edited by another 10 radiation oncologists. RESULTS Three-dimensional descriptions of the lung, proximal bronchial tree, esophagus, spinal cord, ribs, and brachial plexus are presented. Two computed tomography atlases were developed: one for the middle and lower thoracic OARs (except for the heart) and one focusing on the brachial plexus for a patient positioned supine with their arms up for thoracic RT. The dosimetric limits of the key OARs are discussed. CONCLUSIONS We believe these atlases will allow us to define OARs with less variation and generate dosimetric data in a more consistent manner. This could help us study the effect of radiation on these OARs and guide high-quality clinical trials and individualized practice in 3D-conformal RT and stereotactic body RT.

Diffusion MRI: A new strategy for assessment of cancer therapeutic efficacy

The use of anatomical imaging in clinical oncology practice traditionally relies on comparison of patient scans acquired before and following completion of therapeutic intervention. Therapeutic success is typically determined from inspection of gross anatomical images to assess changes in tumor size. Imaging could provide significant additional insight into therapeutic impact if a specific parameter or combination of parameters could be identified which reflect tissue changes at the cellular or physiologic level. This would provide an early indicator or treatment response/outcome in an individual patient before completion of therapy. Moreover, response of a tumor to therapeutic intervention may be heterogeneous. The use of imaging could assist in delineating therapeutic-induced spatial heterogeneity within a tumor mass by providing information related to specific regions that are resistant or responsive to treatment. Largely untapped potential resides in exploratory methods such as diffusion MRI, which is a nonvolumetric intravoxel measure of tumor response based upon water molecular mobility. Alterations in water mobility reflect changes in tissue structure at the cellular level. While the clinical utility of diffusion MRI for oncologic practice is still under active investigation, this overview on the use of diffusion MRI for the evaluation of brain tumors will serve to introduce how this approach may be applied in the future for the management of patients with solid tumors.

Electromyographic and Magnetic Resonance Imaging to Predict Lumbar Stenosis, Low-Back Pain, and No Back Symptoms

BACKGROUND Magnetic resonance imaging is commonly used to diagnose lumbar spinal stenosis. Some persons without symptoms have a small lumbar spinal canal. Electrodiagnosis has been used to diagnose spinal stenosis for over sixty years, but we are aware of no masked, controlled trials of the use of electrodiagnosis for that purpose. This study was performed to evaluate the relationships of magnetic resonance imaging measures and electrodiagnostic data with the clinical syndrome of spinal stenosis. METHODS One hundred and fifty persons between the ages of fifty-five and eighty years old, including asymptomatic volunteers and persons referred for lumbar magnetic resonance imaging, underwent clinical examination, electrodiagnosis, and magnetic resonance imaging. Subjects were excluded if they had neuromuscular disease, sacral cancer, or inadequate test results, which left 126 subjects for the final analysis. The final cohort was divided into three groups--no back pain, mechanical back pain, and clinical spinal stenosis--on the basis of the impression of the examining physician, for whom the results of the magnetic resonance imaging and electrodiagnostic testing were masked. A spine surgeon also reviewed both the imaging and clinical examination data. RESULTS The examining physicians diagnosis of clinical spinal stenosis was significantly related to the neurological findings on examination (p < 0.05) and to the spine surgeons diagnosis (p < 0.001). The diagnosis of clinical spinal stenosis was also significantly related to the presence of fibrillations on electrodiagnostic testing (p < or = 0.003), the minimum anteroposterior diameter of the spinal canal on the magnetic resonance images (p = 0.016), and the average of the two smallest spinal canal diameters (p = 0.008) on the images. Measurements on magnetic resonance imaging did not differentiate subjects with clinical spinal stenosis from controls better than chance, whereas paraspinal mapping electrodiagnosis scores did. CONCLUSIONS This prospective, controlled, masked study of electrodiagnosis and magnetic resonance imaging for older subjects showed that imaging does not differentiate symptomatic from asymptomatic persons, whereas electrodiagnosis does. We believe that radiographic findings alone are insufficient to justify treatment for spinal stenosis.

The sensitivity and specificity of electrodiagnostic testing for the clinical syndrome of lumbar spinal stenosis

Study Design. Prospective, masked, double controlled diagnostic trial. Objectives. To determine the sensitivity and specificity of electrodiagnostic consultation (EDX) for the clinical syndrome of lumbar spinal stenosis. Summary of Background Data. EDX has been used for more than 50 years to diagnose spinal disorders but has not met the new standards of evidence-based medicine. Methods. A total of 150 subjects (asymptomatic volunteers and patients with MRIs suggesting back pain or spinal stenosis; 55–80 years of age) underwent physiatrist history and physical examination, MRI, and review of this data by a neurosurgeon, with each clinician masked to any outside information, leading to a unanimous consensus on diagnosis in 55. After masked EDX testing, 7 subjects with undiagnosed neuromuscular disease were discovered. EDX findings were related to “clinical gold standard” diagnoses in 48 persons. Results. Paraspinal mapping EMG score of >4 had 100% specificity and 30% sensitivity for stenosis compared with either the back pain or asymptomatic groups (each, P < 0.04). A composite limb and paraspinal fibrillation score had a sensitivity of 47.8% and specificity of 87.5% (P = 0.008), and H-wave sensitivity was 36.4, specificity 91.3 (P = 0.026) for stenosis versus all controls. Conclusions. This first masked study in the 60-year history of needle electromyography also introduces anatomically validated needle placement, quantified and reproducible examination of the paraspinal muscles, and dual control populations to EDX research in spinal disorders. EDX has statistically significant, clinically meaningful specificity for spinal stenosis and detects neuromuscular diseases that may masquerade as stenosis.

Spinal canal size and clinical symptoms among persons diagnosed with lumbar spinal stenosis

ObjectiveClinical symptoms associated with lumbar spinal stenosis (LSS) are believed to be due to neurogenic claudication caused by narrowing of the central and lateral spinal canals. However, there is a paucity of published data on these relationships. The purpose of the present study was to examine the relationship between clinical symptoms associated with LSS and osseous anterior-posterior (AP) spinal canal diameter as measured on axial magnetic resonance imaging. DesignCross-sectional study conducted at a University Spine Program. Fifty persons with a clinical diagnosis of LSS were administered measures of clinical pain and perceived function. Walking distance in the laboratory and community was also assessed. Participants also underwent magnetic resonance imaging of the spine. ResultsUsing recommended upper limits from the literature, patients with smaller canals reported greater perceived disability, but no other group differences emerged. In the entire sample, AP spinal canal diameter was not significantly associated with any of the clinical symptom measures examined. Body mass index was found to be significantly related to walking distance, but not perceived function or pain. ConclusionsAP spinal canal diameter is not predictive of clinical symptoms associated with LSS. The findings also suggest that body mass may play a significant role in functional limitations observed in this population.

Does medical school performance predict radiology resident performance

RATIONALE AND OBJECTIVES The authors performed this study to examine the relationship, if any, of a large number of measures of medical school performance with radiology residency performance. MATERIALS AND METHODS Applications of 77 radiology residents enrolled from 1991 to 2000 were reviewed. Medical school grades, deans letter summary statements, letters of recommendation, selection to Alpha Omega Alpha (AOA), and National Board of Medical Examiners (NBME) and U.S. Medical Licensing Examination (USMLE) Step 1 scores were recorded. Student t tests, analysis of variance, and correlation coefficients were used to examine the relationship between these measures of medical school performance and subsequent performance during radiology residency as determined by rotation evaluations, retrospective faculty recall scores, and American College of Radiology (ACR) and American Board of Radiology (ABR) examination scores. Resident performance was also correlated with prestige of the medical school attended. RESULTS Preclinical grades of Honors or A; clinical grades of Honors or A in medicine, surgery, and pediatrics; and high NBME/USMLE scores strongly predicted success on the ABR written clinical examination but did not predict rotation performance. Most other measures of medical school performance, including outstanding Deans letters and letters of recommendation, AOA selection during the senior year, and high medical school prestige did not predict high examination scores or superior rotation performance during residency. CONCLUSION Success on the ABR examination can be predicted by medical school success in preclinical courses, some clinical courses, and USMLE examination scores. Deans letters, letters of recommendation, AOA selection during the senior year, and medical school prestige do not appear to predict future resident performance as reliably.