Variations in T1 and T2 relaxation times of normal appearing white matter and lesions in multiple sclerosis

OBJECTIVE: To investigate the variation in T1 and T2 relaxation times of normal appearing white matter (NAWM) and lesions in multiple sclerosis (MS) throughout the brain. BACKGROUND: The magnetic resonance imaging (MRI) sequence fast FLAIR (fluid attenuated inversion recovery) has demonstrated overall increased lesion detection when compared to conventional or fast spin echo (FSE) but fewer lesions in the posterior fossa and spinal cord. The reasons for this are unknown, but may be due to variations in the T1 and T2 relaxation times within NAWM and MS lesions. METHOD: Ten patients and 10 controls underwent MRI of the brain which involved FSE, fast FLAIR and the measurement of T1 and T2 relaxation times. RESULTS: Of 151 lesions analysed (22 infra-tentorial, 129 supra-tentorial), eight were missed by the fast FLAIR sequence. T1 and T2 relaxation times in normal controls were longer in the infra-tentorial, than supra-tentorial, region. Patient NAWM relaxation times were prolonged compared with control values in both regions. Lesions demonstrated longer relaxation times than either control white matter or patient NAWM in both regions, however this difference was less marked infra-tentorially. The eight posterior fossa lesions not visible on the fast FLAIR sequence were characterised by short T1 and T2 relaxation times which overlapped with the patient NAWM for both T1 and T2 and with control values for T2 relaxation times. CONCLUSION: Both lesion and NAWM relaxation time characteristics vary throughout the brain. The T1 and T2 relaxation times of infra-tentorial lesions are closer to the relaxation times of local NAWM than supra-tentorial lesions, resulting in reduced contrast between posterior fossa lesions and the background NAWM. Consequently the characteristics of some lesions overlap with those of NAWM resulting in reduced conspicuity. By utilising this information, it may be possible to optimise fast FLAIR sequences to improve infra-tentorial lesion detection.     

Do specific neurocognitive deficits predict specific domains of community function in schizophrenia?

We examined whether specific neurocognitive deficits predicted specific domains of community outcome in 40 schizophrenic patients. Neuropsychological assessments were conducted before hospital discharge, and measures of functional outcome were obtained 1 to 3.5 years later. A priori hypotheses were generated based upon a recent review by Green (Green MF [1996] What are the functional consequences of neurocognitive deficits in schizophrenia? American Journal of Psychiatry, 153(3):321-330). As hypothesized, verbal memory predicted all measures of community outcome, vigilance predicted social outcomes, and executive functioning predicted work and activities of daily living (ADLs). However, in addition to the predicted relationships, many other associations were found between neuropsychological test scores and adaptive function. Furthermore, both cognitive and functional measures were intercorrelated. If deficits in adaptive functioning are neurocognitively multi-determined, utilizing compensatory strategies to bypass multiple areas of cognitive impairment may be more efficient than cognitive remediation in improving community outcomes.     

Posttraumatic stress two years after the Oklahoma City bombing in youths geographically distant from the explosion

This article describes Posttraumatic Stress Disorder (PTSD) symptomatology in 69 sixth-grade youths who resided within 100 miles of Oklahoma City at the time of the 1995 bombing of the Alfred P. Murrah Federal Building. These youths neither had any direct physical exposure nor personally knew anyone killed or injured in the explosion. A survey conducted two years after the bombing assessed exposure, PTSD symptoms, and functioning. PTSD symptom frequency was measured with the Impact of Event Scale--Revised. Our BCD criteria for defining PTSD caseness was modeled after DSM-IV B, C, and D criteria requiring one reexperiencing, three avoidance/numbing, and two arousal symptoms for diagnosis. Those who met our BCD criteria had significantly higher PTSD symptom scores than those who did not. Both increased mean PTSD symptom score and meeting our caseness definition were associated with increased functioning difficulties. Media exposure and indirect interpersonal exposure (having a friend who knew someone killed or injured) were significant predictors of symptomatology. These findings suggest that children geographically distant from disaster who have not directly experienced an interpersonal loss report PTSD symptoms and functional impairment associated with increased media exposure and indirect loss.     

MRI of the intraorbital optic nerve in patients with autosomal dominant optic atrophy

Measurements of the intraorbital optic nerve were made using high-resolution coronal MRI in 10 adults with autosomal dominant optic atrophy. Comparisons were made with previous studies of 10 normal adult subjects. The cross-sectional diameters of the optic nerve and the perineural subarachnoid space were measured and a ratio of there diameters at anterior, mid and posterior positions along the optic nerve was determined. We found a statistically significant difference in the mean optic nerve: sheath ratio between the control group and patients with autosomal dominant optic atrophy. At anterior, mid and posterior locations along the optic nerve it is significantly smaller in patients with optic atrophy. We have demonstrated that the loss of ganglion cells, previously documented in dominant optic atrophy, is associated with a significant loss of optic nerve tissue and thinning of the nerve along its length. Received: 6 July 1999/Accepted: 22 July 1999     

Herpesvirus quiescence in neuronal cells: antiviral conditions not required to establish and maintain HSV-2 quiescence

We previously described a novel in vitro model of a non-productive herpes simplex virus type 1 (HSV-1) infection in neurally differentiated (ND)-PC12 cells that allows for inducible virus replication upon forskolin and heat stress (HS) treatment. In this research, we further characterized the model with respect to HSV-2 strain 333. We found that: (i) ND-PC12 cells are non-permissive to HSV-2 replication; (ii) HSV-2 can establish a quiescent infection, like HSV-1, in ND-PC12 cells with the transient use of acycloguanosine (ACV); however unlike HSV-1, anti-viral conditions are not obligatory to establish and maintain a quiescent state; (iii) the quiescent state is maintained in the presence of Vero cell cocultivation indicating that such cultures are free of infectious virus; and (iv) a high percentage of quiescently infected (QIF)-PC12 cell cultures (80 - 100%) produce HSV-2 in response to forskolin and HS (43 degrees C, 3 h) treatment for as long as 4 weeks post infection. These findings indicate that ND-PC12 cells can harbor HSV-2 in a cryptic and non-productive state that is reversible. This model has appealing features for studying gene expression during the establishment, maintenance and reactivation phases of the HSV-2 quiescent state in cell culture.     

Preoperative Evaluation of Pancreatic Masses with Positron Emission Tomography Using 18F-fluorodeoxyglucose: Diagnostic Limitations

Identification of pancreatic cancer in patients presenting with an enlarged pancreatic mass is a major diagnostic problem. Positron emission tomography (PET) using the radiolabeled glucose analogue ¹⁸F-fluorodeoxyglucose (FDG) has been suggested to provide excellent accuracy for noninvasive determination of suspicious pancreatic masses. We conducted a prospective study to verify these results. Forty-two patients admitted for pancreatic surgery underwent PET scanning. Image analysis was based on visual film evaluation and quantification of regional tracer uptake. PET imaging was visually analyzed by three observers blinded for the results of other diagnostic tests; they qualitatively graded the scans using a five-point scale (I = low to V = high) for the presence and intensity of focal FDG uptake. Diagnosis was proven by histology (n= 38) or follow-up (n= 4). Furthermore, the results of PET were compared with helical computed tomography (CT) and conventional ultrasonography (US), done during the routine diagnostic workup before pancreatic cancer surgery. Regarding only the results with scores of IV and V as positive for representing definite malignancy yielded a sensitivity of 71% and a specificity of 64% for film reading. Quantification of regional tracer uptake contributed no significant diagnostic advantage for differentiation between benign and malignant tumors. Helical CT revealed a sensitivity of 74% and a specificity of 45.5% and abdominal US 56% and 50%, respectively. We concluded that PET imaging provides only fair diagnostic accuracy (69%) for characterizing enlarged pancreatic masses. PET does not allow exclusion of malignant tumors. In doubtful cases, the method must be combined with other imaging modalities, such as helical CT. The results indicate that the number of invasive procedures is not significantly reduced by PET imaging.     

Modification of the Penlon Nuffield 200 series ventilator and IPPV with a laryngeal mask airway

There is a risk of regurgitation if a laryngeal mask airway is used with intermittent positive pressure ventilation. The lower the pressure gradient between airway and stomach, the less will be the likelihood of stomach insufflation with gas and consequent regurgitation. A flow generator ventilator, such as the Penlon Nuffield 200 which achieves a peak pressure at the end of inspiration at any given tidal volume, is likely to produce a higher peak airway pressure than a pressure generator. Replacing the expiratory valve by a venturi gives a preferable flow pattern with an inspiratory pressure plateau. At equal tidal volumes, the venturi modification provided a 10% lower inflation pressure (standard deviation 6%, P < 0.01) and a 1.8% smaller leak (P < 0.05) past the laryngeal mask airway. The same comparison but using identical inflation pressures, gave 8% larger tidal volumes (standard deviation 5.1%, P < 0.01) and a 2% smaller leak (P < 0.01) past the laryngeal mask airway.     

Pressure mapping of the radioulnar carpal joint: effects of ulnar lengthening and wrist position

The purpose of this study was to investigate the effects of ulnar lengthening and wrist position on force transmission through the radioulnar carpal joint in a forced dorsiflexed wrist position. Eight cadaveric arms were subjected to a 30 kg compressive load directed down the forearm towards the wrist. A pressure sensor recorded forces across the wrist joint with the triangular fibrocartilage complex intact and excised. The biomechanics of the distal radioulnar joint were altered by changes in ulnar length and wrist position. Pressures at the ulnolunate articulation increased as the ulna was lengthened and were significantly lower when the triangular fibrocartilage complex was excised. An inverse relationship between triangular fibrocartilage complex thickness and ulnar variance was shown. Greater increases in ulnolunate pressure were observed in more positive ulnar variant wrists.