Antti E. Lamminen

Magnetic resonance imaging of primary skeletal muscle diseases: patterns of distribution and severity of involvement

Magnetic resonance imaging of the lower extremities was performed with a low field system in 51 patients representing three different categories of biopsy-proven primary skeletal muscle disease; muscular dystrophies, congenital myopathies and polymyositis. The intermuscular distribution of abnormal signal intensity and the grade of involvement of individual muscles were assessed. Large differences in the degree of pathological signal intensity between individual muscles were found in all categories. In the muscular dystrophy and polymyositis patients, the overall involvement was significantly more severe than in patients with congenital myopathy. Definite patterns of selective involvement were seen. Statistical evidence of selective muscle sparing was found; the gracilis muscle was significantly less affected than the other muscles in all three disease groups. Other muscles with significant sparing include the rectus femoris and sartorius muscles of the thigh and the tibialis posterior muscle of the leg. Common anatomical and functional characteristics of muscles may be related to the distribution of muscular disease.

Acute rhabdomyolysis: evaluation with magnetic resonance imaging compared with computed tomography and ultrasonography.

Fifteen patients with acute rhabdomyolysis were evaluated with low field magnetic resonance (MR) imaging and the results compared with those obtained using computed tomography (CT) and ultrasonography (US). With MR imaging, abnormal muscles with areas of increased signal intensity were seen in every patient, which probably reflects increased water content or increased mobility of water molecules caused by inflammatory reaction and oedema in the injured and necrotic muscles. Computed tomography without intravenous contrast medium demonstrated abnormal muscles in most patients examined with this modality. The CT findings consisted of areas of focal hypodensity in muscles. With US, abnormal muscles were seen in less than half of the patients studied. The normal structure of striated muscle was focally disturbed and areas of both decreased and increased echogenicity were found. Magnetic resonance imaging had a higher sensitivity in the detection of abnormal muscles than CT or US (100%, 62% and 42%, respectively). The findings of all these modalities are non-specific, but together with the clinical and laboratory data they confirm the diagnosis of rhabdomyolysis. The information gained from imaging studies is useful in the assessment of the extent and distribution of rhabdomyolysis. The precise identification of affected muscle compartments by MR imaging is valuable when surgical fasciotomy is considered for treatment; the procedure can then be appropriately directed to the compartments with clearly abnormal muscles.

MRI of rotator cuff muscle atrophy in relation to glenohumeral joint incongruence in brachial plexus birth injury

Purpose: To evaluate rotator cuff muscles and the glenohumeral (GH) joint in brachial plexus birth injury (BPBI) using MRI and to determine whether any correlation exists between muscular abnormality and the development of glenoid dysplasia and GH joint incongruity. Materials and methods: Thirty-nine consecutive BPBI patients with internal rotation contracture or absent active external rotation of the shoulder joint were examined clinically and imaged with MRI. In the physical examination, passive external rotation was measured to evaluate internal rotation contracture. Both shoulders were imaged and the glenoscapular angle, percentage of humeral head anterior to the middle of the glenoid fossa (PHHA) and the greatest thickness of the subscapular, infraspinous and supraspinous muscles were measured. The muscle ratio between the affected side and the normal side was calculated to exclude age variation in the assessment of muscle atrophy. Results: All muscles of the rotator cuff were atrophic, with the subscapular and infraspinous muscles being most severely affected. A correlation was found between the percentage of humeral head anterior to the middle of the glenoid fossa (PHHA) and the extent of subscapular muscle atrophy (rs=0.45, P=0.01), as well as between its ratio (rs=0.5, P P=0.01). Severity of rotator cuff muscle atrophy correlated with increased glenoid retroversion and the degree of internal rotation contracture. Conclusions: Glenoid retroversion and subluxation of the humeral head are common in patients with BPBI. All rotator cuff muscles are atrophic, especially the subscapular muscle. Muscle atrophy due to neurogenic damage apparently results in an imbalance of the shoulder muscles and progressive retroversion and subluxation of the GH joint, which in turn lead to internal rotation contracture and deformation of the joint.

T1ρ dispersion imaging of diseased muscle tissue

Abstract T1ρ dispersion, or the frequency dependence of T1 relaxation in the rotating frame, was used for in vivo muscle tissue characterization in 13 patients with primary skeletal muscle disease and in eight normal subjects for comparison. T1ρ dispersion measurements represent a new approach to magnetic resonance tissue characterization, possibly reflecting the macromolecular constituents of tissue. A definite, statistically significant, difference was found between the relative T1ρ dispersion values of normal and diseased muscle tissue. T1ρ dispersion measurements and images may increase the accuracy of identification of diseased muscles. Early identification of affected muscles is important for accurate diagnosis by muscle biopsy.

Parathyroid Hormone Treatment Improves Pain and Fracture Healing in Adult Hypophosphatasia

INTRODUCTION Adult hypophosphatasia (HPP) is characterized by low serum alkaline phosphatase (S-ALP) and poorly healing fractures due to ALPL gene mutations. Increased S-ALP and fracture repair were reported in two patients treated with teriparatide, PTH 1-34. The effects of full-length PTH 1-84 have not been studied. METHODS Two 56- and 64-yr-old sisters (patients 1 and 2) with HPP and with long-standing, painful femur fractures received PTH 1-84 (Preotact, 100 μg/d sc) for 7 and 18 months, respectively. Patient 1 had another treatment 8 months later because of new femur fractures. We characterized the underlying mutation(s) and treatment effects according to S-ALP, bone markers, serum ionized calcium, plasma phosphate (P-Pi), pain, mobility, and fracture healing. RESULTS Both patients were compound heterozygotes for a p.G339R and p.E191K ALPL mutation. S-ALP increased significantly, 4.9- and 6.8-fold in patient 1 and 2.7-fold in patient 2. Responses decreased at 6 months but remained higher than basal activity. Serum N-terminal propeptide of type I procollagen and urinary N-telopeptide of type I collagen increased 14- to 19-fold and 9-5-fold in patient 1, respectively, and 9- and 3-fold in patient 2. P-Pi fluctuated in patient 1 and increased in patient 2. Pain and mobility improved promptly. Fractures healed after 7-8 months of treatment in patient 1 and at 15 months in patient 2. CONCLUSION PTH 1-84 improves pain, mobility, and fracture repair in adult HPP, even after repeat treatment. Residual activity of the p.E191K ALPL gene mutation could explain why PTH can stimulate S-ALP. P-Pi concentrations may modulate the response.

Magnetic resonance of diseased skeletal muscle: combined T1 measurement and chemical shift imaging

Magnetic resonance examinations of skeletal muscle with differential T1 relaxation time measurements were performed in 19 patients with muscular dystrophies and congenital myopathies, and in eight control subjects. A field echo chemical shift imaging technique was used. T1 values of muscular tissue were measured from the primary composite images, and differential T1 values were calculated separately from water and fat images. Longitudinal relaxation times of skeletal muscle were significantly increased in both dystrophies and myopathies. The results of differential relaxation time measurements suggest that intramuscular fat reduces the abnormal increase in T1 of diseased muscle tissue. When characterizing diseases of skeletal muscle by T1 relaxation time measurements, the contribution of secondary fatty infiltration must be considered.

Comparison of high-field magnetic resonance imaging with computed tomography in the evaluation of blunt renal trauma

OBJECTIVE To compare magnetic resonance (MR) imaging and computed tomography (CT) in radiographic staging of blunt renal trauma. DESIGN A prospective study. MATERIALS AND METHODS Fourteen patients with blunt renal trauma not requiring early surgical treatment underwent CT, and high-field (1.0 T) MR imaging. MEASUREMENTS AND MAIN RESULTS MR imaging equaled CT in correctly grading the renal injury. The coronal and sagittal projections of MR imaging were helpful in determining the extent of the renal parenchymal lesion. Both methods were accurate in finding perirenal hematomas, assessing the viability of renal fragments, and detecting pre-existing renal abnormalities, but failed to visualize urinary extravasation on initial examination. CONCLUSIONS Although CT remains the method of choice in radiographic staging of renal injury, MR imaging can complement CT in patients with severe renal injury, pre-existing renal abnormality, equivocal CT findings, or when repeated radiographic follow-up is required. MR imaging could replace CT in patients with iodine allergy and be used for initial staging if CT is not available.

Imaging of congenital esophageal cysts in adults

The radiologic imaging of esophageal cysts (EC) in adults is described. These rare cysts, often detected incidentally on routine chest radiographs, seldom produce symptoms, but they may cause precordial sensations, arrhythmias, and dysphagia. They may also bleed and become malignant. As surgical excision is the treatment of choice, the preoperative diagnosis must be exact. For this, magnetic resonance imaging (MRI) or endoscopic ultrasound seem to be the imaging methods of choice even if a plausible diagnosis can be advanced on computed tomography (CT). Chest x-ray or esophagus roentgenogram have little differential diagnostic value.

Detection of focal liver lesions with superparamagnetic iron oxide: value of STIR and SE imaging

Objective We assessed the value of superparamagnetic iron oxide (SPIO) particles on the detection of focal liver lesions by MRI. Materials and Methods Twenty patients with one to five focal liver lesions, primarily detected with ultrasonography and/or contrast-enhanced CT, were evaluated further with unenhanced and iron oxide-enhanced MRI at 1.0 T. Superparamagnetic iron oxide particles were administered intravenously as a slow infusion. Then T1-, T2-, and proton density–weighted SE images were obtained. In addition, the performance of a short T1 inversion recovery (STIR) sequence was evaluated. Results The iron oxide contrast medium had marked effects on liver signal-to-noise (S/N) and tumor-to-liver contrast-to-noise (C/N) ratios but only minimal effects on tumor S/N ratios in cases of malignant tumor foci. Lesion-to-liver contrast, expressed as differences between the tumor and liver S/N ratios, improved very significantly after SPIO infusion with all four pulse sequences. Contrast enhancement of the liver parenchyma was best in T2-weighted SE images, but the tumor-to-liver C/N values were highest with the postcontrast STIR sequence. The SPIO enhancement revealed a number of additional focal lesions (31%), also foci under 1 cm in diameter. In three benign focal lesions, SPIO infusion produced a definite reduction in the S/N ratio of the lesions in contrast to the minimal change measured in malignant foci. The favorable performance of the STIR sequence contradicts the disappointing results previously obtained at 0.6 T. Conclusion Superparamagnetic iron oxide is a promising new contrast medium for MR examinations of the liver, increasing the conspicuity and reducing the detectability threshold of focal hepatic lesions.

MRI and CT in blunt renal trauma : An update

In our experience, MRI is as effective as CT in correctly staging renal injury. The coronal and sagittal slice orientations of MRI are particularly helpful in determining the extent of the renal parenchymal damage. Both methods are accurate in finding perirenal hematomas, assessing the viability of renal fragments, and detecting preexisting renal abnormalities but are relatively inaccurate in visualizing urinary extravasation. Although CT remains the method of choice in radiological staging of renal injury, MRI can complement CT in patients with severe renal injury, preexisting renal abnormality, equivocal CT findings, or when repeated radiological follow-up is required. MRI could replace CT in patients with iodine allergy and be used for initial staging if CT is not available.