Alpay Alkan

Evaluation of in vivo cerebral metabolism on proton magnetic resonance spectroscopy in patients with impaired glucose tolerance and type 2 diabetes mellitus

The aim of this study was to investigate possible metabolic alterations in cerebral tissues on magnetic resonance spectroscopy (MRS) in patients with impaired glucose tolerance (IGT) and with type 2 diabetes mellitus (T2-DM). Twenty-five patients with T2-DM, 13 patients with IGT, and 14 healthy volunteers were included. Single-voxel spectroscopy (TR: 2000 ms, TE: 31 ms) was performed in all subjects. Voxels were placed in the frontal cortex, thalamus, and parietal white matter. N-acetylaspartate (NAA)/creatine (Cr), choline (Cho)/Cr, and myo-inositol (MI)/Cr ratios were calculated. Frontal cortical Cho/Cr ratios were increased in patients with IGT compared to control subjects. Parietal white matter Cho/Cr ratios were significantly higher in patients with IGT when compared to patients with T2-DM. In the diabetic group, frontal cortical MI/Cr ratios were increased, and parietal white matter Cho/Cr ratios were decreased when compared to the control group. Frontal cortical NAA/Cr and Cho/Cr ratios and parietal white matter Cho/Cr ratios were decreased in diabetic patients with poor glycemic control (A1C>10%). A1C levels were inversely correlated with frontal cortical NAA/Cr and Cho/Cr ratios and with parietal white matter Cho/Cr ratios. T2-DM and IGT may cause subtle cerebral metabolic changes, and these changes may be shown with MRS. Increased Cho/Cr ratios may suggest dynamic change in membrane turnover in patients with IGT. Diabetic patients with poor glycemic control may be associated with neuronal dysfunction/damage in brain in accordance with A1C levels and, in some, extend with insulin resistance.

Diffusion‐weighted images differentiate benign from malignant thyroid nodules

To reveal the possible role of diffusion‐weighted images (DWI) in the differential diagnosis of benign and malignant thyroid nodules by comparing the results of fine‐needle aspiration cytology (FNAC).

Duplication of the abducens nerve at the petroclival region. An anatomic study

OBJECTIVEDuring its course between the brainstem and the lateral rectus muscle, the abducens nerve usually travels forward as a single trunk, but it is not uncommon for the nerve to split into two branches. The objective of this study was to establish the incidence and the clinical importance of the duplication of the nerve. METHODSThe study was performed on 100 sides of 50 autopsy materials. In 10 of 11 cases of duplicated abducens nerve, colored latex was injected into the common carotid arteries and the internal jugular veins. The remaining case was used for histological examination. RESULTSFour of 50 cases had duplicated abducens nerve bilaterally. In seven cases, the duplicated abducens nerve was unilateral. In 9 of these 15 specimens, the abducens nerve emerged from the brainstem as a single trunk, entered the subarachnoid space, split into two branches, merged again in the cavernous sinus, and innervated the lateral rectus muscle as a single trunk. In six specimens, conversely, the abducens nerve exited the pontomedullary sulcus as two separate radices but joined in the cavernous sinus to innervate the lateral rectus muscle. In 13 specimens, both branches of the nerve passed beneath the petrosphenoidal ligament. In two specimens, one of the branches passed under the ligament and the other passed over it. In one of these last two specimens, one branch passed over the petrosphenoidal ligament and the other through a bony canal formed by the petrous apex and the superolateral border of the clivus. In all of the specimens, both branches were wrapped by two layers: an inner layer made up of the arachnoid membrane and an outer layer composed of the dura during its course between their dural openings and the lateral wall of the cavernous segment of the internal carotid artery. This finding was also confirmed by histological examination in one specimen. CONCLUSIONDouble abducens nerve is not a rare variation. Keeping such variations in mind could spare us from injuring the VIth cranial nerve during cranial base operations and transvenous endovascular interventions.

Evaluation of the gluteus medius muscle after a pelvic support osteotomy to treat congenital dislocation of the hip

BACKGROUND Many authors have reported that the pelvic support osteotomy prevents a Trendelenburg gait by restoring the biomechanics of the abductor muscle in patients with congenital dislocation of the hip. However, we are not aware of any studies in which the hip abductor muscles were examined following pelvic support osteotomy. The purpose of this study was, first, to use magnetic resonance imaging to measure alterations in the length and volume of the gluteus medius muscle after pelvic support osteotomy and, second, to determine which factors influence the results of the Trendelenburg test. METHODS Eleven patients with a history of congenital hip dislocation who had been treated with a pelvic support osteotomy were examined clinically with the Harris hip score and the Trendelenburg test, radiographically to measure limb-length discrepancy and valgus angulation of the proximal part of the femur, and with magnetic resonance imaging to measure changes in the gluteus medius length and volume. RESULTS The pelvic support osteotomy achieved a functional and painless hip in all eleven patients. Five of the eleven patients had a persistently positive Trendelenburg gait at the time of the last follow-up visit, at an average of three years after the osteotomy. The muscle volumes were restored to 43% to 89% of the muscle volumes on the normal contralateral side, and the postoperative muscle volume correlated significantly with the result of the Trendelenburg test (r = -0.63; p = 0.03). There was a positive association between age and the result of the Trendelenburg test (p = 0.01): four of the five patients who had a positive test were at least thirty-one years of age at the time of the operation. There was no correlation between the Trendelenburg test and the change in the length of the gluteus medius muscle, which averaged 19.2 mm in the patients with a positive test and 19.3 mm in those with a negative test. CONCLUSIONS Patient age at the time of the operation and the postoperative change in the volume of the gluteus medius muscle have a significant influence on the result of the Trendelenburg test after a pelvic support osteotomy. Moreover, our study demonstrated that restoration of the muscle volume after a pelvic support osteotomy is not sufficient to prevent a Trendelenburg gait in older patients with congenital dislocation of the hip. LEVEL OF EVIDENCE Therapeutic Level IV.

MRI findings in thoracic outlet syndrome

We discuss MRI findings in patients with thoracic outlet syndrome (TOS). A total of 100 neurovascular bundles were evaluated in the interscalene triangle (IS), costoclavicular (CC), and retropectoralis minor (RPM) spaces. To exclude neurogenic abnormality, MRIs of the cervical spine and brachial plexus (BPL) were obtained in neutral. To exclude compression on neurovascular bundles, sagittal T1W images were obtained vertical to the longitudinal axis of BPL from spinal cord to the medial part of the humerus, in abduction and neutral. To exclude vascular TOS, MR angiography (MRA) and venography (MRV) of the subclavian artery (SA) and vein (SV) in abduction were obtained. If there is compression on the vessels, MRA and MRV of the subclavian vessels were repeated in neutral. Seventy-one neurovascular bundles were found to be abnormal: 16 arterial–venous–neurogenic, 20 neurogenic, 1 arterial, 15 venous, 8 arterial–venous, 3 arterial–neurogenic, and 8 venous–neurogenic TOS. Overall, neurogenic TOS was noted in 69%, venous TOS in 66%, and arterial TOS in 39%. The neurovascular bundle was most commonly compressed in the CC, mostly secondary to position, and very rarely compressed in the RPM. The cause of TOS was congenital bone variations in 36%, congenital fibromuscular anomalies in 11%, and position in 53%. In 5%, there was unilateral brachial plexitis in addition to compression of the neurovascular bundle. Severe cervical spondylosis was noted in 14%, contributing to TOS symptoms. For evaluation of patients with TOS, visualization of the brachial plexus and cervical spine and dynamic evaluation of neurovascular bundles in the cervicothoracobrachial region are mandatory.

Microanatomical architecture of dorello's canal and its clinical implications

OBJECTIVE We investigated the membranous architecture of the abducens nerve at the petroclival region and describe the characteristics of this area in cadaveric specimen and two children with hydrocephalus and sixth nerve palsy using magnetic resonance imaging (MRI). MATERIALS AND METHODS Five adult cadaver heads were used to investigate the petroclival part of the abducens nerve. The heads were injected with colored latex for microsurgical dissection, and the length of the dural sleeve of the abducens nerve and its width at the apex were measured. In one cadaver head, the area between the petroclival entrance porus of the abducens nerve and the cavernous sinus was histologically studied under light microscopy. In two patients with hydrocephalus and abducens nerve palsy, the petroclival area was screened by using the MRI fat suppression technique. RESULTS In the cadavers, the arachnoid membrane on the clivus extended within the dural sleeve as far as the petrous apex, as an extension of the subarachnoid space. The average length of the dural sleeve was 9.5 mm and the average width was 1.5 mm at the apex, where the nerve entered the cavernous sinus. MRI scans showed that the cerebrospinal fluid distance of the petroclival region was 5 mm in the first patient and 7 mm in the second. CONCLUSION The subarachnoid space inside the dural sleeve of the abducens nerve can be defined by using thin-slice MRI scans. Enlargement of the dural sleeve at the petroclival region may coexist with the abducens nerve palsy. It has been documented in this study that the arachnoid membrane forms a membraneous barrier between the subarachnoid and subdural spaces within Dorellos canal.

Delayed myelination in a rhizomelic chondrodysplasia punctata case: MR spectroscopy findings

Rhizomelic chondrodysplasia punctata is a member of genetic peroxisomal disorders. Delayed myelination, which is probably related to the inadequacy of plasmalogens biosynthesis, is an important feature of this disorder. Direct assessment of neuropathologic aspects of RCDP syndrome such as neuronal degeneration and delayed myelination is possible with MR spectroscopy. In this report, MR spectroscopy findings (decreased Cho/Cr and increased Ins-Gly/Cr ratios and increased levels of mobile lipids) of a rhizomelic chondrodysplasia punctata case supporting delayed myelination are presented. This is the second report of MR spectroscopy examination of the specific brain metabolic changes associated with rhizomelic chondrodysplasia punctata.

Metabolic Changes in Pelvic Lesions: Findings at Proton MR Spectroscopic Imaging

Objective: The purpose of this study is to investigate the in vivo magnetic resonance spectroscopic (MRS) features of pelvic lesions using long echo time and to characterize the spectral patterns of various pathological entities. Materials and Methods: 17patients with surgically and histopathologically confirmed pelvic lesions underwent long echo-time MRS, and the results obtained were analyzed. Before laparotomy, choline (Cho), lactate, lipid and creatine (Cr) levels of all lesions were measured by single voxel MRS (point-resolved spectroscopy technique, TE 136 ms). Voxels were placed in the center of the lesions. The MRS results of lesions were compared with the final histopathological diagnoses. Results: Spectroscopy analysis of serous, mucinous and undifferentiated carcinoma of the ovary revealed Cho, lactate and lipid signals, but granulosa-theca cell tumor showed only a lipid signal. The Cho signal was obtained from only 3 patients with mature cystic teratoma but none of the other benign ovarian tumors and pelvic abscesses. A lipid signal was detected in 3 patients diagnosed with pelvic abscess and all benign ovarian tumors. In addition to the lipid signal, a lactate signal was detected in the spectra of two pelvic abscesses. One case of endometrioma and 1 case of teratoma did not show any signal. Conclusion: MRS demonstrates significant differences in metabolite concentration between benign and malignant ovarian tumors and pelvic abscesses. MRS may therefore be helpful in the differential diagnosis of adnexal lesions.

The role of MRS in the differentiation of benign and malignant soft tissue and bone tumors

OBJECTIVE The aim of our study was to investigate the value of choline in the discrimination of benign and malignant soft tissue and bone tumors. MATERIALS AND METHODS The study group consisted of thirty subjects with bone or soft tissue tumors larger than 1.5 cm in diameter. The experiments were performed in a 1.5T MR scanner. Coils were selected according to specific locations. A single-voxel MRS was performed for three different TE (time to echo) (31, 136, 272 ms). The volume of interest was positioned on the brightest enhancement. The presence of a cholin peak on at least 2 of these spectrums was considered as the marker of malignancy. The sensitivity, specificity and accuracy of the MRS in the detection and diagnosis of malignant lesions were calculated. The reproducibility of MRS and histopathological results were tested with kappa statistics. RESULTS Histopathologically, 18 (60%) of the lesions were classed as malignant whereas 12 (40%) were classed as benign. With MRS, 15 (50%) of these lesions were classed as malignant and 15 (50%) as benign. Two patients who were found spectroscopically to have malignant tumors were shown histopathologically to have benign types. Five patients with an MRS showing a benign type were classed with malignant types in histopathological examinations. MRS had a sensitivity rate of 72.2%, specificity of 83.3%, and an accuracy rate of 76.6% in detecting malignant bone and soft tissue tumors. The interrater reliability of both techniques had a kappa value of 0.533. CONCLUSIONS MRS may help in the differentiation of benign and malignant soft tissue and bone tumors.

Early MRI findings in stab wound of the cervical spine: two case reports

Abstract. MR imaging was found to be the most sensitive modality for the detection of spinal cord abnormalities in the acutely injured spine. Although it is reported that traumatic pneumomyelogram indicates a base-of-skull or middle cranial fossa fracture and is almost certainly associated with intracranial subarachnoid air, early MR imaging may demonstrate subarachnoid air in penetrating trauma of the spinal cord without head injury. We report two cervical-spine stab-wound cases, one of which had subarachnoid air on early MR findings.