Kohki Yoshikawa

A Functional MRI study on the neural substrates for writing

Functional neuroanatomy of writing is relatively unknown compared to that of other linguistic processes. This study aimed at identifying brain regions crucial to the process of writing. Using functional magnetic resonance imaging (fMRI), brain hemodynamic activity was examined during three conditions that differentially engaged visual, linguistic, and/or motor functions: (1) writing names of pictures with the right index finger, (2) naming pictures silently, and (3) visually cued finger tapping. A writing minus naming comparison and a writing minus tapping comparison were performed, and brain regions commonly activated in these two contrasts were detected. Our main finding was that such common activation was observed in the anterior part of the left superior parietal lobule, the posterior part of the middle and superior frontal gyri, and the right cerebellum. The parietal and frontal regions were considered to subserve the process of writing as separated from that of naming and finger movements, which is consistent with the classical notion mainly proposed by studies of selective writing deficits called pure agraphia. The right cerebellar activation, on the other hand, was interpreted as the reflection of the execution of complex finger movements required for writing. Hum. Brain Mapping 13:34–42, 2001.

Magnetic Resonance Imaging and Magnetic Resonance Myelography in the Presurgical Diagnosis of Lumbar Foraminal Stenosis

Study Design. Retrospective case series with a control group. Objective. To measure the diagnostic performance of magnetic resonance imaging (MRI) and MR myelography (MRM) for symptomatic foraminal stenosis in patients who need surgery. Summary of Background Data. MR images are extensively used in the evaluation of foraminal stenosis and are often used to evaluate nerves exiting from the foramen. There has been no published report of the diagnostic performance of these imaging methods (MRI and MRM). Methods. Diagnostic performances were studied in 90 patients in whom the site of the stenosis was confirmed by means of selective decompression surgeries. The disease prevalence among patients was 26% (23 of 90 patients). The disease prevalence among foramens was 3% (25 of 936 foramens). The prevalence of abnormal findings in 27 asymptomatic volunteers was also studied. Two blinded observers interpreted foraminal narrowing on combinations of sagittal and axial MR images, abnormalities of the course of the nerve root in the foramen, and spinal nerve swelling on MRM. Results. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of MRI for the diagnosis of symptomatic foraminal stenosis were 96%, 67%, 4%, and 100%, respectively. The corresponding values for abnormal nerve root course on MRM were 96%, 83%, 7%, and 100%, respectively, and for spinal nerve swelling on MRM were 60%, 99%, 35%, and 99%, respectively. Conclusions. Compared with conventional MRI, MRM affords more specific information for the presurgical diagnosis of symptomatic foraminal stenosis.

In vivo imaging of spin-trapped nitric oxide in rats with septic shock: MRI spin trapping

This paper reports the first in vivo NMR image of the distribution of NO using the “MRI spin‐trapping” technique. NO was complexed with the Fe(II)‐chelate spin trap, N‐methyl‐d‐glucamine dithiocarbamate (MGD), verified as (MGD)2‐Fe(II)‐NO by EPR, and the radical distribution was “visualized” by MR images. In rats, the (MGD)2‐Fe(II)‐NO complex was concentrated in the liver displaying significantly enhanced contrast in the vascular structure such as hepatic vein and inferior vena cava. Nitric oxide synthase was verified as the source of NO in rats with septic shock by pre‐administration of the competitive inhibitor N‐monomethyl‐l‐arginine, resulting in reduced enhancement. The NO complex was more stable in vivo and a more effective MRI contrast agent than other stable nitrogen containing radicals, such as nitroxides. The MRI spin‐trapping method should be a powerful tool for visualizing spatial distributions of free radicals in pathologic organs and tissues when combined with the appropriate radical complexing agent, such as (MGD)2‐Fe(II) used in these studies. Magn Reson Med 42:235–239, 1999.

Neural substrates for the recognition of newly learned faces: a functional MRI study

Face recognition is critical to the appreciation of our social and physical relations. Functional magnetic resonance imaging (fMRI) was used to identify brain regions involved in the recognition of newly learned faces. Two experiments were conducted. Experiment 1 contrasted a fixation control task with a face recognition task in which subjects were exposed solely to previously viewed faces (all-target). Experiment 2 compared a fixation control with another face recognition task in which subjects were presented with both novel and viewed faces (half-target). Compared to the fixation control, the all-target face recognition was associated with activation in the bilateral occipital and occipitotemporal regions, whereas the half-target face recognition produced activation in the right parietal and prefrontal regions, in addition to the occipital and occipitotemporal. The all-target minus half-target comparison revealed significant activation in the bilateral fusiform gyrus, suggesting stronger fusiform activity during the all-target than the half-target face recognition. The half-target minus all-target comparison showed significant activation in the superior and inferior parietal lobules and several regions in the right frontal lobe. These findings demonstrated that the bilateral fusiform gyrus is involved, not only in face perception, but in a certain aspect of face recognition memory and that this aspect is related to the actual recognition of previously viewed faces rather than the processing of novel ones, which results are consistent with previous lesion work. The right parietal and frontal regions, in contrast, are differentially more associated with the processes related to the detection of novel faces or retrieval effort.

Functional magnetic resonance imaging (fMRI) during mental writing with phonograms

Functional magnetic resonance imaging (fMRI) at 1.5 T using a gradient echo echo-planar sequence was employed to identify brain regions activated during the performance of a mental writing task using phonograms. Four regions were activated in all six subjects; the region surrounding the left intraparietal sulcus, the region surrounding the middle part of the left precentral sulcus and the posterior part of the left superior frontal sulcus, the region surrounding the right intraparietal sulcus, and the region surrounding either or both of the left and right cingulate sulci. The left intraparietal region was usually the most extensively activated. The results suggest that these four regions particularly the left intraparietal region, are essential in writing with phonograms. Since the left hemisphere was more extensively activated than the right, fMRI during the mental writing task is a good candidate for determining non-invasively which hemisphere is dominant for language.

Dorsal root ganglia morphologic features in patients with herniation of the nucleus pulposus: assessment using magnetic resonance myelography and clinical correlation.

Study Design. Morphologic features of the dorsal root ganglia were investigated in patients with herniation of the nucleus pulposus by means of magnetic resonance myelography. Objectives. This study was undertaken to assess morphologic changes of the dorsal root ganglia in patients with herniation of the nucleus pulposus and to determine the relations between the morphologic features of the dorsal root ganglia and clinical features. Summary of Background Data. It has recently been reported that application of the nucleus pulposus to a nerve root induces edema in the rat dorsal root ganglion. Edema in the human dorsal root ganglion resulting from lumbar disc herniation has not been discussed in the literature, to the authors’ knowledge. Methods. Eighty-three consecutive patients (average age 42.1 years; range 17 to 77 years) with monoradicular symptoms were examined. Dorsal root ganglion morphologic features, i.e., indentations and swelling, were evaluated by magnetic resonance myelography. The dorsal root ganglion swelling at each level was quantitatively expressed as a ratio of the dorsal root ganglion width on the involved side to that of the contralateral side and was termed dorsal root ganglion ratio. Eighty-three uninvolved levels were chosen as controls in a randomized manner. Factors possibly contributing to the morphologic changes in the dorsal root ganglion were investigated. Neurologic symptoms, evaluated by the Japan Orthopaedic Association scoring system, were correlated to the morphologic changes. The morphologic features were followed up for 1 year after treatment in a small group of patients. Results. Dorsal root ganglion indentations were always found in the narrowed intervertebral foramens. The incidence of indentations was significantly higher at the involved nerve roots (10.8%) than at the uninvolved nerve roots (4.0%) (P = 0.026). Patients with dorsal root ganglion indentations were significantly older (P = 0.0008). Leg pain scores in patients with indentations were significantly poor (P = 0.007). The dorsal root ganglion ratios were significantly higher at the involved levels than at the uninvolved levels (P = 0.001); the means ± SD were 1.19 ± 0.25 and 1.08 ± 0.13, respectively. Patients with lateral herniated nucleus pulposus had significantly higher dorsal root ganglion ratios than those with central herniated nucleus pulposus (P = 0.0001); the mean ratios ± SD were 1.48 ± 0.32 and 1.10 ± 0.12, respectively. A moderate positive correlation was found between dor-sal root ganglion ratio and age (Pearson’s correlation coefficient = 0.313). There was moderate negative correlation between the dorsal root ganglion ratio and leg pain, gait, motor, and total Japan Orthopaedic Association score (correlation coefficients were = −0.385, −0.350, −0.422, and −0.358, respectively). The dorsal root ganglion ratios were significantly diminished at 1-year follow-up (P = 0.001); the means ± SD were 1.22 ± 0.22 and 1.09 ± 0.07, respectively. Indentations observed before treatment disappeared after treatment. Conclusions. Swelling and impingement in the involved dorsal root ganglion were clearly visualized by magnetic resonance myelography. The swelling and indentations were well correlated with severity of leg pain. These findings have important value in understanding the pathophysiology of the nerve roots in herniated nucleus pulposus.

Presurgical identification of extradural nerve root anomalies by coronal fat-suppressed magnetic resonance imaging: a report of six cases and a review of the literature.

In an attempt to depict the anatomy of the nerve roots, we obtained magnetic resonance (MR) images of the lumbar spine in the coronal plane with the frequency-selective fat-suppression technique. With this technique, extradural anomalies were identified in 20 (6.7%) of 300 patients. We report the appearance on coronal MR images of six surgically confirmed extradural anomalous nerve roots together with the myelography findings. These include type Ia, type Ib, and type 3 anomalies. These are readily recognized and allow detailed evaluation of the type of nerve root anomaly.

Clinical late phase II trials of MultiHance (Gd-BOPTA) for the magnetic resonance imaging of liver tumors in Japan.

OBJECTIVEnThe purpose of the study was to evaluate the safety and efficacy of Gd-BOPTA for liver imaging and to determine the most appropriate clinical dose to administer.nnnMETHODSnGd-BOPTA was administered at a dose of 0.05 (group A), 0.1 (group B), or 0.2 (group C) mmol/kg to 201 patients suspected of having malignant liver tumors who had been referred for magnetic resonance imaging. Dynamic phase images (T1-weighted gradient echo sequences obtained during breath-hold), images obtained within 10 min of Gd-BOPTA injection (spin echo images) and delayed images obtained at 40-120 min after Gd-BOPTA injection (T1-weighted spin echo and gradient echo sequences during breathhold) were acquired. All post-contrast images were compared with pre-contrast images (T1- and T2-weighted sequences) obtained immediately prior to Gd-BOPTA administration. Safety was assessed in terms of the incidence of adverse events.nnnRESULTSnThe contrast efficacy for the dynamic study was classified as ( ) in 39.7% (27/68), 55.4% (36/65), and 47.0% (31/66) for groups A, B, and C, respectively. The contrast efficacy within 10 min of the injection was classified as ( ) in 7.6% (5/66), 16.9% (11/65), and 12.5% (8/64) for groups A, B, and C, respectively. The contrast efficacy at 40-120 min post-injection was classified as ( ) in 4.4% (3/68), 21.5% (14/65), and 20.0% (13/65) for groups A, B, and C, respectively with significant differences noted between groups A and B and groups A and C. As regards safety, the overall incidence of adverse reactions was 3.5% (7/199).nnnCONCLUSIONnGd-BOPTA is a safe and efficacious contrast agent for use in both dynamic phase imaging and delayed (40-120 min) static imaging. A dose of 0.1 mmol/kg Gd-BOPTA appears to be the ideal dose for use in liver imaging in Japan.

Pedunculated bronchogenic cyst mimicking pleural lesion.

We report a rare case of a bronchogenic cyst presenting as a pleural nodule. CT and MRI demonstrated a well circumscribed, homogeneous lesion located on the pleural surface apart from the mediastinum. It was proven to be a bronchogenic cyst localized between the parietal and visceral pleurae and connected with the mediastinum only through fibrous tissue. Radiologists should be aware that a mediastinal bronchogenic cyst may be located apart from the mediastinum.

Focal Hepatic Lesions on Magnetic Resonance Imaging Induced by Trimethoprim/Sulfamethoxazole in HIV Infection

TO THE EDITOR: Trimethoprim/sulfamethoxazole (TMP/SMX) is an agent preferentially used for the prophylaxis of Pneumocystis carinii infection in patients with HIV whose CD4+ cell counts are ≤200 cells/mm3.1 Severe skin rash (20%), hepatitis (20%), neutropenia (15%), and thrombocytopenia (15%) were observed as the most frequent major reactions associated with TMP/SMX treatment for P. carinii pneumonia.2 We report a case of focal hepatic lesions that were determined by magnetic resonance imaging (MRI) and induced by TMP/SMX, which was administered for the prophylaxis of P. carinii infection. Case Report. A 35-year-old Japanese man with hemophilia A and HIV-1 infection was given TMP/SMX (160 mg/800 mg) three times a week for the primary prophylaxis of P. carinii pneumonia for two years because of CD4+ lymphocyte cell counts <200 cells/mm3. He had experienced transient rash without fever two times after the administration of TMP/SMX. The rash disappeared several days later without medication. Although he was also seropositive for hepatitis C virus, abnormal serum alanine aminotransferase values (ALT, 10 IU/L) and episodes of hepatitis had not been observed. We had previously administered the antiretroviral agents zidovudine 300 mg/d and didanosine 250 mg/d for seven months; stavudine 60 mg/d and ritonavir 800 mg/d were then given for nine months. Erythema with itching developed on his hands. Two days later, he was admitted to the hospital because the rash had extended to his trunk and he had a temperature of 38.5 ̊C. TMP/SMX and antiretroviral agents were discontinued. On hospital day 3, the rash was worse and temperature was 40.3 ̊C; oral administration of prednisolone 30 mg/d was initiated. Laboratory findings showed elevated serum ALT 47 IU/L (normal 0–30), alkaline phosphatase 355 IU/L (70–290), lactate dehydrogenase 615 IU/L (240–430), γ-glutamyl transpeptidase 348 IU/L (0–40), total bilirubin 1.5 mg/dL (0–0.4), Creactive protein 3.12 mg/dL (0–0.25), and reduction of prothrombin activity 55% (80–120). On hospital day 4, abdominal ultrasonography showed a hypoechoic space–occupying lesion in the medial segment of the liver. An MRI of the liver, with dynamic enhancement by contrast material, was performed by using a 1.5-T scanner, GE-Signa Horizon 5.5v (Signa, General Electric Medical Systems, Milwaukee, WI), on hospital day 10. T1-weighted spin-echo MRIs (TR/TE, 400/9) revealed two ill-defined and irregular mass lesions (diameters of 30 and 20 mm), with low-signal intensity in the posterior and medial segments of the liver. The same lesions had higher signal intensity than liver parenchyma in the axial planes on the T2-weighted fast spin-echo images (TR/TE, 8571/90) (Figure 1). Postcontrast images by gadolinium indicated only delayed enhancement of the mass lesions. No rapid washout of contrast material was noted. The radiologic impression of these MRI results was that they were neoplastic lesions, such as Kaposi’s sarcoma. Erythema disappeared slowly, and the corticosteroid therapy was tapered off by hospital day 15. A follow-up study of the hepatic MRI obtained on hospital day 17 showed size reduction of the two mass lesions, and the patient was discharged from the hospital. The mass lesion in the medial segment had disappeared on the MRI one month later, and the lesion in the posterior segment did so two months later. The hepatic biopsy could not be performed. At the same time, follow-up data in the concentration of serum ALT was 8 IU/L, so stavudine 60 mg/d, lamivudine 300 mg/d, ritonavir 600 mg/d, and saquinavir 800 mg/d were given for approximately nine months. He did not receive TMP/SMX because of increased CD4+ lymphocyte cell count (>300 cells/mm3). A recent MRI of the liver indicated normal findings about 14 months after the development of the focal hepatic lesions. The concentration of serum ALT obtained at the same time was within normal range (13 IU/L). Because of these clinical episodes, laboratory data indicative of inflammation, and the effects of corticosteroid therapy, we believe that focal mass lesions on the MRI of the liver were inflammatory pseudotumors induced by TMP/SMX. LETTERS