Gunnar Moen

MRI assessment of the alar ligaments in the late stage of whiplash injury – a study of structural abnormalities and observer agreement

Abstract. Our aim was to characterise and classify structural changes in the alar ligaments in the late stage of whiplash injuries by use of a new MRI protocol, and to evaluate the reliability and the validity of this classification. We studied 92xa0whiplash-injured and 30xa0uninjured individuals who underwent proton density-weighted MRI of the craniovertebral junction in three orthogonal planes. Changes in the alar ligaments (gradesxa00–3) based on the ratio between the high signal area and the total cross-sectional area were rated twice at a 4-month interval, independently by three radiologists. Inter- and intraobserver statistics were calculated by ordinary and weighted kappa. Cases classified differently were reviewed to identify potential causes for disagreement. The alar ligaments were satisfactorily demonstrated in all cases (244xa0ligaments in 122xa0individuals). The lesions, 2–9xa0years after the injury, varied from small high-signal spots to high signal throughout the cross-sectional area. Signal was highest near the condylar insertion in 82 of 94xa0ligaments, indicating a lesion near that insertion, and near the dental insertion in eight, indicating a medial lesion. No gradexa02 or 3 lesion was found in the control group. At least two observers assigned the same grade to 214xa0ligaments (87.7%) on the second occasion. In 30xa0ligaments (12.3%) this agreement was not obtained. Pair-wise interobserver agreement (weighted kappa) was fair to moderate (0.31–0.54) in the first grading, improving to moderate (0.49–0.57) in the second. Intraobserver agreement (weighted kappa) was moderate to good (0.43–0.70). Whiplash trauma can cause permanent damage to the alar ligaments, which can be shown by high-resolution proton density-weighted MRI. Reliability of classification of alar ligament lesions needs to be improved.

MR analysis of the transverse ligament in the late stage of whiplash injury.

Purpose: To analyse and classify structural changes in the transverse ligament in the late stage of whiplash injury by use of high-resolution MRI, and to evaluate the reliability of our classification. Material and Methods: Ninety-two whiplash-injured (2–9 years previously, mean 6 years) and 30 non-injured individuals underwent proton-weighted MR imaging of the craniovertebral junction in three orthogonal planes. Structural changes in the transverse ligaments were graded twice (grades 1–3) based on increased signal, independently by 3 radiologists with a 4-month interval. Inter- and intraobserver statistics were calculated by ordinary and weighted kappa (K). Results: Image quality was excellent in 109 cases and slightly reduced in 13. Twenty-two out of 30 ligaments in the control group were classified as normal (73%) compared with only 32 out of 92 in the injured group (36%). Two or all 3 observers agreed in their grading in 101 out of 122 ligaments (83%). Intraobserver agreement (weighted K) was fair to good (0.33–0.73). Pair-wise interobserver agreement was fair (0.24–0.39). Reasons for divergent grading were insufficient knowledge of normal variations, low signal intensity in the peridental soft tissue obscuring the ligament and interpretation flaw. Conclusion:Whiplash trauma can damage the transverse ligament. By use of high-resolution proton-weighted MR images such lesions can be detected and classified. The reliability of this classification still needs improvement.

Localized cerebral energy failure in DNA polymerase gamma-associated encephalopathy syndromes

Mutations in the catalytic subunit of the mitochondrial DNA-polymerase gamma cause a wide spectrum of clinical disease ranging from infantile hepato-encephalopathy to juvenile/adult-onset spinocerebellar ataxia and late onset progressive external ophthalmoplegia. Several of these syndromes are associated with an encephalopathy that characteristically shows episodes of rapid neurological deterioration and the development of acute cerebral lesions. The purpose of this study was to investigate the nature, distribution and natural evolution of central nervous system lesions in polymerase gamma associated encephalopathy focusing particularly on lesions identified by magnetic resonance imaging. We compared radiological, electrophysiological and pathological findings where available to study potential mechanisms underlying the episodes of exacerbation and acute cerebral lesions. We studied a total of 112 magnetic resonance tomographies and 11 computed tomographies in 32 patients with polymerase gamma-encephalopathy, including multiple serial examinations performed during both the chronic and acute phases of the disease and, in several cases, magnetic resonance spectroscopy and serial diffusion weighted studies. Data from imaging, electroencephalography and post-mortem examination were compared in order to study the underlying disease process. Our findings show that magnetic resonance imaging in polymerase gamma-related encephalopathies has high sensitivity and can identify patterns that are specific for individual syndromes. One form of chronic polymerase gamma-encephalopathy, that is associated with the c.1399G > A and c.2243G > C mutations, is characterized by progressive cerebral and cerebellar atrophy and focal lesions of the thalamus, deep cerebellar structures and medulla oblongata. Acute encephalopathies, both infantile and later onset, show similar pictures with cortical stroke-like lesions occurring during episodes of exacerbation. These lesions can occur both with and without electroencephalographic evidence of concurrent epileptic activity, and have diffusion, spectroscopic and histological profiles strongly suggestive of neuronal energy failure. We suggest therefore that both infantile and later onset polymerase gamma related encephalopathies are part of a continuum.

Acoustic neuroma-treatment modalities : Surgery, gamma-knife or observation ?

We present our results of 211 patients with acoustic neuroma over a period of 10 years, 1988-97. We operated on 100 and 111 had Gamma-knife (GK) treatment (69 were available to follow-up). The results are excellent for surgery on small and intracanalicular tumours. In tumours of the same size, surgery and GK treatment give comparable, but somewhat different, results. In the GK group of 54 primary treated patients, 3 patients had to be operated on and another 4 developed hydrocephalus. A group of 35 acoustic tumours was observed for more than 3 years. Nineteen did grow (54%). Hearing was unchanged in 23%. We performed surgery in 11 patients and gave 2 patients GK treatment because of tumour growth of >2 mm in diameter a year. We conclude that either treatment is effective for small and medium-sized acoustic neuromas. Hearing preservation was best in the GK-treated group (80%), compared to only 12.5% in the group operated via the suboccipital route. Larger tumours and most medium-sized tumours should be operated, as should smaller tumours with persistent symptoms of vertigo and pain. Medical contraindications to surgery or reluctance to undergo surgery make GK treatment a good alternative. Treatment of residual tumours with the GK could also be a solution to a difficult problem.

Cerebral diffusion and perfusion deficits in North Sea divers

Background: Diving is associated with a risk of cerebral decompression illness, and the prevalence of neurological symptoms is higher in divers compared with control groups. Microvascular dysfunction due to gas microembolism and exposure to hyperoxia are possible mechanisms, which may result in cerebral diffusion and perfusion deficits. Purpose: To investigate if possible functional derangements of the microvasculature and microstructure would be more prevalent among symptomatic divers. Material and Methods: Magnetic resonance imaging (MRI) was performed in 91 former divers and 45 controls. Individual parametric images of apparent diffusion coefficient (ADC), cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT) were generated on the basis of diffusion- and perfusion-weighted imaging. To identify regions with statistically significant differences between groups (P < 0.05, corrected for false discovery rate), voxel-wise ANCOVA analysis was performed for each of the four parametric images. Results: Significant regional group differences were found in all four parametric comparisons. Gross regional ADC differences were seen throughout the brain, including large frontal and temporal white-matter regions, the hippocampus, and parts of the cerebellum. Differences in the perfusion maps were localized in fewer and smaller clusters, including parts of the cerebellum, the putamen, and the anterior watershed regions. Conclusion: Regional functional abnormalities as measured by diffusion- and perfusion-weighted imaging were identified in the divers, and there was a partial co-localization of the regions identified in the perfusion and the diffusion images. The findings may explain some of the long-term clinical symptoms reported among professional divers.

Clinical presentation and diffusion weighted MRI of acute cerebral infarction. The Bergen Stroke Study

BackgroundNo large study has compared the yield of diffusion-weighted imaging (DWI) with clinical examination in order to differentiate lacunar stroke from other stroke subtypes. This differentiation is important for guiding further investigations and treatment.MethodsConsecutive patients admitted with cerebral infarction were classified according to the Oxfordshire Community Stroke Project scale. Based on DWI and CT stroke was classified as lacunar (LI) and non-lacunar (NLI). Acute ischemic lesion <1.5 cm and located in subcortex or in brainstem were classified as LI. All other infarctions were classified as NLI.ResultsDWI was performed in 419 (69%) patients. Among patients with lacunar syndrome (LACS) 45 (40.5%) had NLI on DWI. All patients with total anterior syndrome (TACS) and 144 (88.3%) with partial anterior syndrome (PACS) had NLI on DWI.ConclusionDWI is important among patients presenting with clinical symptoms suggestive of lacunar syndrome to differentiate between LI and NLI. On the other hand, there is good correspondence between TACS or PACS and NLI on DWI.

Magnetic resonance brain perfusion imaging with voxel-specific arterial input functions

To propose an automatic method for estimating voxel‐specific arterial input functions (AIFs) in dynamic contrast brain perfusion imaging.

Pseudoprogression in high-grade glioma.

Pseudoprogression is a treatment‐related effect seen on imaging in high‐grade glioma. Enhancement of gadolinium contrast on control MRI can be misinterpreted as tumor recurrence and is also difficult to distinguish from radiation necrosis. Pseudoprogression is seen in up to 30% after standard treatment for glioblastoma multiforme (GBM), which is radiotherapy concurrent with chemotherapy with temozolomide (TMZ) and adjuvant cycles of TMZ. In this article, the current literature on pseudoprogression in high‐grade glioma is reviewed by searches in PubMed. We also present two clinical cases, one of which had medullary pseudoprogression. No articles on this subentity of pseudoprogression were found in PubMed. Standard MRI with gadolinium contrast cannot differentiate between pseudoprogression, tumor recurrence and radiation necrosis. More advanced imaging techniques are often not available. Pseudoprogression seems to be related to methylated promoter of the O6‐ methyl‐guanine methyl transferase (MGMT) gene, which is associated with improved treatment effect. Discontinuation or change of therapy on the basis of misinterpretation of MRI as disease progression is thus unfortunate. MRI should be interpreted with caution the first 6 months after standard treatment of high‐grade glioma. In a GBM patient with contrast enhancement on MRI but few or no new symptoms and/or stable steroid doses, treatment should be continued and control imaging performed after 2–3 months.

A population-based study of neurosurgical and endovascular treatment of ruptured, intracranial aneurysms in a small neurosurgical unit.

OBJECTIVESince the introduction of endovascular embolization, the optimal treatment of ruptured aneurysms has been debated. Much of this debate has been based on results from large neurovascular centers and may not be applicable to small neurosurgical centers with low annual aneurysm loads. We think that the results of small centers, such as ours, may also be of some interest. METHODSThis study included 286 patients treated endovascularly or operated on by the senior investigator (KW) before November 2004. They all had an angiographically verified aneurysm as the source of bleeding in the subarachnoid hemorrhage. Variables related to presentation, radiological findings, treatment, and outcome were recorded. RESULTSA significantly higher proportion (66.3%) of the endovascular patients had complete or near-complete recovery (Glasgow Outcome Scale 5) compared with the surgically treated patients (47.8%). When clinical outcomes were dichotomized into favorable (Glasgow Outcome Scale 4–5) and unfavorable (Glasgow Outcome Scale 1–3), no difference was found between the two treatment groups. Treatment-related mortality or morbidity was equal. Significantly more patients were converted from endovascular to surgical treatment than vice versa. No surgically treated patients rebled, whereas four endovascular patients rebled from their previously treated aneurysm. CONCLUSIONAt present in our hospital, the endovascular modality seems to yield a better clinical outcome than surgery and has become our treatment of choice. With increasing use and further refinement of the endovascular techniques, the difference in outcomes between the treatment modalities will probably change even further in favor of the endovascular technique.

Laminarthrectomy as a surgical approach for decompressing the spinal canal: assessment of preoperative versus postoperative dural sac cross-sectional areal (DSCSA)

IntroductionSurgery for lumbar spinal stenosis (LSS) is today the most frequently performed procedure in the adult lumbar spine. Long-term benefit of surgery for LSS is well documented both in randomized and in non-randomized trials. In this paper, we present the results from laminarthrectomy as an alternative surgical approach, which have theoretical advantages over other approaches. In this study, we wanted to study the clinical and radiological results of laminarthrectomy. Dural sac cross-sectional areal (DSCSA) is an objective method to quantify the degree of central stenosis in the spinal canal, and was used to measure whether we were able to achieve an adequate decompression of the spinal canal with laminarthrectomy as a surgical approach.Materials and methodsAll patients operated on with this approach consecutively in the period 1 January 2008 to 31 March 2009 were included in the study. All perioperative complications were noted. Clinical results were measured by means of a questionnaire. The patients that agreed to attend the study had an MRI taken of the operated level. DSCSA before and after surgery of the actual level were measured by three observers. We then performed a correlation test between increase of area and clinical results. We also tested for inter- and intra-observer reability.ResultsFifty-six laminarthrectomy were performed. There were 17xa0% complications, none of them were life-threatening or disabling. 46 patients attended the study and answered the questionnaire. Thirty-four patients (83xa0%) reported clinical improvement, whereas six (13xa0%) patients reported no improvement, and two (4xa0%) patients reported that they were worse. Mean ODI was 23.0. Mean EQ-5D was 0.77. Mean VAS-score for back-pain was 3.1 and mean VAS-score for leg-pain was 2.8. Mean DSCSA were measured to 80xa0mm2 before surgery and 161xa0mm2 after surgery. That gave an increase of DSCSA of 81xa0mm2 (101xa0%). We found a significant positive correlation between increase of area and clinical results. We also found consistent inter- and intra-observer reability.DiscussionIn this study, the clinical results of laminarthrectomy were good, and comparable with other reports for LSS. The rates of complications are also comparable with other reports in spinal surgery. A significant increase in the spinal canal diameter was achieved. Within the limitations a retrospective study gives, we conclude that laminarthrectomy seems to be a safe and effective surgical approach for significant decompressing the adult central spinal canal, and measurement of DSCSA, before and after surgery seems to be a good way to quantify the degree of decompression.