Donald H. Lee

Identification of Penumbra and Infarct in Acute Ischemic Stroke Using Computed Tomography Perfusion–Derived Blood Flow and Blood Volume Measurements

Background and Purpose— We investigated whether computed tomography (CT) perfusion–derived cerebral blood flow (CBF) and cerebral blood volume (CBV) could be used to differentiate between penumbra and infarcted gray matter in a limited, exploratory sample of acute stroke patients. Methods— Thirty patients underwent a noncontrast CT (NCCT), CT angiography (CTA), and CT perfusion (CTP) scan within 7 hours of stroke onset, NCCT and CTA at 24 hours, and NCCT at 5 to 7 days. Twenty-five patients met the criteria for inclusion and were subsequently divided into 2 groups: those with recanalization at 24 hours (n=16) and those without (n=9). Penumbra was operationally defined as tissue with an admission CBF <25 mL · 100 g−1 · min−1 that was not infarcted on the 5- to 7-day NCCT. Logistic regression was applied to differentiate between infarct and penumbra data points. Results— For recanalized patients, CBF was significantly lower (P<0.05) for infarct (13.3±3.75 mL · 100 g−1 · min−1) than penumbra (25.0±3.82 mL · 100 g−1 · min−1). CBV in the penumbra (2.15±0.43 mL · 100 g−1) was significantly higher than contralateral (1.78±0.30 mL · 100 g−1) and infarcted tissue (1.12±0.37 mL · 100 g−1). Logistic regression using an interaction term (CBF×CBV) resulted in sensitivity, specificity, and accuracy of 97.0%, 97.2%, and 97.1%, respectively. The interaction term resulted in a significantly better (P<0.05) fit than CBF or CBV alone, suggesting that the CBV threshold for infarction varies with CBF. For patients without recanalization, CBF and CBV for infarcted regions were 15.1±5.67 mL · 100 g−1 · min−1 and 1.17±0.41 mL · 100 g−1, respectively. Conclusions— We have shown in a limited sample of patients that CBF and CBV obtained from CTP can be sensitive and specific for infarction and should be investigated further in a prospective trial to assess their utility for differentiating between infarct and penumbra.

Endoscopic carpal tunnel release: A cadaveric study

Five surgeons performed endoscopic (Dyonics) carpal tunnel releases on 24 fresh cadaver wrists. In 50% of the specimens, transection of the transverse carpal ligament was incomplete. The average amount of incomplete release was 31% (range, 0% to 53%). Three types of incomplete release were noted: (1) release of Guyons canal release--one, (2) incomplete distal ligament release--five, and (3) incomplete central or superficial release--six. Other technical errors were noted in nine of 24 specimens. There were no nerve lacerations. Endoscopic carpal tunnel release is either a technically demanding procedure, commonly results in incompletely released ligaments, or both. Proper training, followed by practice on several cadaver specimens before its clinical use, is recommended.

White Matter Thresholds for Ischemic Penumbra and Infarct Core in Patients with Acute Stroke: CT Perfusion Study

PURPOSE To prospectively determine the parameters derived at admission computed tomographic (CT) perfusion imaging admission that best differentiate ischemic white matter that recovers from that which infarcts, with the latter retrospectively defined at a CT examination performed without contrast material (unenhanced CT) 5-7 days after the event. MATERIALS AND METHODS Ethics committee approval and informed consent were obtained. Thirty patients with stroke underwent unenhanced CT, CT angiography, and CT perfusion studies at admission. Additionally, CT angiography was performed 24 hours after the stroke, and an unenhanced CT study was performed 5-7 days after the stroke. Five patients were excluded; the remaining patients (10 men, 15 women; mean age, 70 years +/- 13 [standard deviation]) were separated into those with recanalization (n = 16) and those without recanalization (n = 9) at 24 hours. For patients with recanalization, the final infarct was outlined on unenhanced CT images obtained 5-7 days after the event and was superimposed on coregistered maps from the CT perfusion study performed at admission. Ischemic white matter tissue (cerebral blood flow [CBF] < 14 mL/min/100 g) was identified at the admission CT perfusion study, and the penumbra was defined as the difference between the ischemic region and the infarct region. RESULTS Infarct regions showed a matched decrease in CBF and cerebral blood volume (CBV) at admission, whereas penumbra regions showed a significant (P < .05) decrease in CBF but no change in CBV (P > .05) from contralateral values. A threshold CBF . CBV value of 8.14 was the most sensitive (95%, 20 of 21 regions) and specific (94%, 32 of 34 regions) parameter for differentiating between regions of ischemic white matter that recovered and regions of ischemic white matter that infarcted. CONCLUSION The product of CBF and CBV derived from CT perfusion data provided the best differentiation between regions of ischemic white matter that infarcted and regions of ischemic white matter that recovered 5-7 days after a stroke.

Transient lesion in the splenium of the corpus callosum in an epileptic patient

Pathogenesis of a rarely occurring transient, isolated focal lesion of the splenium of the corpus callosum in epilepsy patients is uncertain: frequent seizures or antiepileptic drug reduction causing ischemia or demyelination is possible. The several MRI sequences, including diffusion-weighted imaging, in this first case of occipital epilepsy suggest ischemia from rapid carbamazepine reduction, frequent seizures, or a combination of both.

Corticosteroid injections in the treatment of trigger finger: a level I and II systematic review.

Abstract Trigger finger is a tendinitis (stenosing tenosynovitis) with multiple management approaches. We conducted an evidencebased medicine systematic review of level I and II prospective randomized controlled trials to determine the effectiveness of corticosteroid injection in managing trigger finger. MEDLINE, Cochrane database, and secondary references were reviewed to locate all English‐language prospective randomized controlled trials evaluating trigger finger treatment. Four studies using injectable corticosteroids were identified, based on the following inclusion criteria: all were prospective randomized controlled trials of adults with >85% follow‐up. This review indicates that the incidence of trigger finger is greatest in women (75%), with an average patient age range of 52 to 62 years. Combined analysis of these four studies shows that corticosteroid injections are effective in 57% of patients.

Precontoured Fixed-Angle Volar Distal Radius Plates: A Comparison of Anatomic Fit

PURPOSE To compare distal radius volar fixed-angle plates for anatomic fit. METHODS Twenty embalmed radii were stripped of soft tissues. The volar lip (watershed line) on the volar distal radius served as a reference line. Seven volar fixed-angle plates were tested (Acumed Acu-loc Standard, Hand Innovations DVRAW and DVRAN, Synthes Juxta-articular [JA], Synthes Extra-articular [EA], Trimed Volar Bearing, Zimmer Volar Lateral Column). Four parameters of anatomic fit were studied: (1) site of best fit; (2) percent plate contact; (3) pin-subchondral bone distance; and (4) extraosseous penetrations. The Wilcoxon signed rank test and Pearsons correlation coefficient were used to compare interobserver plate placement. A Kruskal-Wallis analysis of variance was used to compare percent plate contact and pin-subchondral bone distance across all plates. The Bonferroni correction for multiple comparisons was used to compare pin-subchondral bone distances for all possible plate combinations. RESULTS There was no difference between observers for plate placement. Each plate had a specific site of best fit, and the 7 plates varied widely in best fit location. Percent contact (range, 3% to 6%) between plates was significantly different. Pin-subchondral bone distance across all plates was significantly different. Analysis of all possible plate combinations showed that the Synthes EA pin-subchondral bone distances were significantly different than those of all plates except Zimmer. Amongst the 140 plate insertions, the radiocarpal joint was penetrated in 17, the styloid in 7, (with 6 associated with the DVRAW plate), and the distal radioulnar joint in 9 (all associated with the DVRAW plate). CONCLUSIONS There was considerable variation in ideal plate location among the 7 plates tested. Total contact was minimal for all plates tested. The Synthes EA pin-subchondral bone distance was significantly greater than those of other plates tested. Joint penetration was relatively common, necessitating use of fluoroscopy and proper plate width.

Bipolar shoulder arthroplasty.

Bipolar shoulder arthroplasty was designed as a salvage procedure for the arthritic shoulder with a massive rotator cuff tear. Between 1985 and 1989, 14 patients were treated with a bipolar shoulder arthroplasty and were followed for a mean of 3.3 years (range, 2-4.8 years). Two patient populations were studied, including: (1) rheumatoid patients undergoing a primary shoulder arthroplasty, and (2) reconstructive patients undergoing a secondary reconstructive procedure. The rheumatoid group had overall good pain relief. The average postoperative active forward flexion, abduction, and external rotation was 79 degrees, 66 degrees, and 20 degrees, respectively. The reconstructive group had fair pain relief, with an average postoperative active forward flexion, abduction, and external rotation of 39 degrees, 44 degrees, and 12 degrees, respectively. Six of seven complications were noted in the reconstructive group, including two bipolar cup dislocations, one bipolar cup subluxation, and one loosening of the prosthesis. The factors associated with complications included absence of an intact subacromial arch and deltoid abnormality. The bipolar shoulder arthroplasty appears to be an alternative to a primary arthroplasty for the arthritic rheumatoid shoulder with a massive rotator cuff tear.

Hemodynamic instability during carotid artery stenting: the relative contribution of stent deployment versus balloon dilation.

OBJECT Hemodynamic instability may complicate carotid angioplasty and stenting in up to 40% of patients. The authors have previously demonstrated that primary self-expanding stent placement alone can gradually dilate severely stenosed carotid arteries without the use of balloons. The authors hypothesized that eliminating the balloon would reduce carotid baroreceptor stimulation, thereby decreasing the incidence of hemodynamic instability. METHODS Ninety-seven high surgical risk patients with symptomatic, severely stenosed carotid arteries were treated with the intention of using a self-expanding stent alone. Seventy-seven arteries (79%) were treated with stenting alone, and 20 required angioplasty (21%). RESULTS Intraprocedural bradycardia (heart rate < 60 bpm) developed in 29 patients (38%) and hypotension (systolic blood pressure < 90 mm Hg) occurred in 1 patient (1%) treated with stenting alone. Fourteen patients (70%) who underwent angioplasty and stenting had bradycardia, and hypotension developed in 4 (20%). Atropine, glycopyrrolate, or vasopressors were required in 8% of patients who received stenting alone, compared to 30% of patients who underwent angioplasty. In the first 24 hours after treatment, hypotension or bradycardia developed in 25 patients (32%) who had undergone stent placement alone, and in 15 patients (75%) after stent placement and balloon angioplasty. There was no difference in the occurrence of intra- or postprocedural hypertension (systolic blood pressure > 160 mm Hg) between patients treated with stenting alone or stenting and balloons. Factors independently associated with hemodynamic depression included baseline heart rate and balloon use. CONCLUSIONS Hemodynamic instability during and after carotid artery stenting was observed more frequently when balloon angioplasty was required than when stent placement was performed without concurrent balloon angioplasty.

Brain blood flow in the neurological determination of death: Canadian expert report.

The neurological determination of death (NDD, brain death) is principally a clinical evaluation. However, ancillary testing is required when there are factors confounding the clinical determination or when it is impossible to complete the minimum clinical criteria. At the time of the 2003 Canadian Forum clarifying the criteria for brain death, 4-vessel cerebral angiography or radionuclide angiography were the recommended tests and the electroencephalogram was no longer supported. At the request of practitioners in the field, the Canadian Council for Donation and Transplantation sponsored the assembly of neuroradiology and neurocritical care experts to make further recommendations regarding the use of ancillary testing. At minimum, patients referred for ancillary testing should be in a deep unresponsive coma with an established etiology, in the absence of reversible conditions accounting for the unresponsiveness and the clinical examination should be performed to the fullest extent possible. For newborns, children and adults, demonstration of the absence of brain blood flow by following recommended imaging techniques fulfill the criteria for ancillary testing: 1. radionuclide angiography or CT angiography 2. traditional 4-vessel angiography 3. Magnetic resonance angiography or Xenon CT. In the absence of neuroimaging, an established cardiac arrest, as defined by the permanent loss of circulation, fulfills the ancillary criteria for the absence of brain blood flow. Acknowledging the existing limitations in this field, further research validating current or evolving techniques of brain blood flow imaging are recommended.

Clinical nerve conduction and needle electromyography studies.

Abstract The electrodiagnostic study, consisting of nerve conduction studies and needle electromyography, is a useful adjunct to the clinical examination of the peripheral nervous system. The three types of nerve conduction study are motor, sensory, and mixed, of which motor is the least sensitive. Electromyography records the intrinsic electrical activity of muscle fibers, thus providing the physiologic status of muscle function. To interpret the electrodiagnostic study results, the clinician must understand the anatomic and physiologic basis of the studies. Peripheral nerve entrapment initially results in focal demyelination; thus, nerve conduction velocity slows across the site. However, with radiculopathy and nerve root compression, the nerve conduction study may be normal. Both nerve trauma and polyneuropathy show marked differences in their effect on the results of electrodiagnostic studies.