Yukihiko Fujii, Naoki Nakayama and Tsutomu Nakada
Because of the high signal-to-noise (S/N) ratio, T2-weighted images obtained using high-field magnetic resonance (MR) imaging systems can be expected to provide high anatomical and contrast resolution. Furthermore, the improved structural and contrast resolution of these high S/N T2-weighted images can be processed for optimum perceptual resolution through the application of gray-scale reversal and expansion of the gray-scale window, known as T2-reversed (T2R) imaging. In this study, the authors investigated high-resolution T2R MR imaging performed on a high-field (3-tesla) system for its clinical utility in detecting various physiological and pathological conditions.
Takatoshi Sorimachi, Yukihiko Fujii, Naoto Tsuchiya and Masatsune Saito
✓ The authors report on two patients in whom an increased signal on T1-weighted magnetic resonance images and a high-density signal on computerized tomography scans of the striatum were demonstrated, both of which were associated with nonketotic hyperglycemia. Involuntary movements, which have been present in all previously reported cases, were not observed in either patient at any time during the entire course of illness. One patient displayed hemiparesis, whereas the other had dementia, gait disturbance, and urinary incontinence. Clinical and radiological abnormalities improved on control of blood glucose levels. Invasive studies, including biopsy procedures, should be avoided on encountering this disease given the good prognosis that results from simple medical treatment.
Yukihiko Fujii and Tsutomu Nakada
Object. A systematic investigation on cortical reorganization in patients with hemiparesis of a subcortical origin, with special emphasis on functional correlates, was conducted using functional magnetic resonance (fMR) imaging performed on a 3-tesla system specifically optimized for fMR imaging investigation.
Methods. The study group included 46 patients with hemiparesis (25 with right and 21 with left hemiparesis) and 30 age-matched healthy volunteers as controls. All study participants were originally right handed. The characteristics of the lesion were putaminal hemorrhage in 19 patients, thalamic hemorrhage in 10 patients, and striatocapsular bland infarction in 17 patients.
Functional recovery in subcortical hemiparesis showed two distinct phases of the recovery process involving entirely different neural mechanisms. Phase I is characterized by the process of recovery and/or reorganization of the primary system. Successful recovery of this system is typically reached within 1 month after stroke onset. Its clinical correlate is a rapid recovery course and significant recovery of function within 1 month of stroke onset. Failure of recovery of the primary system shifts the recovery process to Phase II, during which reorganization involving the ipsilateral pathway takes place. The clinical correlate of Phase II is a slow recovery course with variable functional outcome.
Conclusions. Effective functional organization of the ipsilateral pathway, as identified by linked activation of the ipsilateral primary sensorimotor cortex and contralateral anterior lobe of the cerebellum, is correlated with a good prognostic outcome for patients in the slow recovery group. A high degree of connectivity between supplementary motor areas, bilaterally, appears to influence functional recovery adversely.
Takatoshi Sorimachi, Yukihiko Fujii and Takeo Nashimoto
Tsutomu Nakada, Yukihiko Fujii and Ingrid L. Kwee
Object. The authors investigated brain strategies associated with hand use in an attempt to clarify genetic and nongenetic factors influencing handedness by using high-field functional magnetic resonance imaging.
Methods. Three groups of patients were studied. The first two groups comprised individuals in whom handedness developed spontaneously (right-handed and left-handed groups). The third group comprised individuals who were coercively trained to use the right hand and developed mixed handedness, referred to here as trained ambidexterity. All trained ambidextrous volunteers were certain that they were innately left-handed, but due to social pressure had modified their preferred hand use for certain tasks common to the right hand.
Although right-handed and left-handed volunteers displayed virtually identical cortical activation, involving homologous cortex primarily located contralateral to the hand motion, trained ambidextrous volunteers exhibited a clearly unique activation pattern. During right-handed motion, motor areas in both hemispheres were activated in these volunteers. During left-handed motion, the right supplemental motor area and the right intermediate zone of the anterior cerebellar lobe were activated significantly more frequently than observed in naturally right-handed or left-handed volunteers.
Conclusions. The results provide strong evidence that cortical organization of spontaneously developed right- and left-handedness involves homologous cortex primarily located contralateral to the hand motion, and this organization is likely to be prenatally determined. By contrast, coerced training of the nondominant hand during the early stages of an individual's development results in mixed handedness (trained ambidexterity), indicating cortical reorganization.
Masafumi Fukuda, Makoto Oishi, Tetsuya Hiraishi, Manabu Natsumeda and Yukihiko Fujii
The authors retrospectively analyzed various clinicopathological factors to determine which are related to regrowth during a long-term follow-up period in patients who underwent incomplete vestibular schwannoma (VS) resection.
This study involved 74 patients (25 men and 49 women) in whom a VS was treated surgically via the lateral suboccipital approach, and who had postoperative follow-up periods exceeding 5 years. The mean follow-up was 104.1 months (range 60–241 months), and the mean patient age at surgery was 48.1 years (range 19–75 years). The tumors ranged in size from 0 mm (localized within the internal auditory canal) to 56 mm (28.3 ± 12.2 mm [mean ± SD]).
Gross-total resection (GTR) was performed in 41 (55%) of the 74 patients; subtotal resection ([STR]; 90–99%) in 25 (34%); and partial resection ([PR]; < 90%) in 8 (11%). Regrowth rates in the GTR, STR, and PR groups were 2.4% (1 of 41 cases), 52% (13 of 25), and 62.5% (5 of 8), respectively, and the times to regrowth ranged from 6 to 76 months (median 31.9 months). The regrowth-free survival curves differed significantly between the complete (GTR) and incomplete (STR and PR) resection groups. Eighteen (54.5%) of the 33 patients who underwent incomplete resection showed evidence of regrowth during follow-up. Univariate and multivariate analyses of various factors revealed that both the thickness of the residual tumor, based on MR imaging after surgery, and the MIB-1 index were positively related to residual tumor regrowth. The receiver operating characteristic curves, plotted for both the thickness of the residual tumor and the MIB-1 index, identified the optimal cutoff points for these values as 7.4 mm (sensitivity 83.3%, specificity 86.7%) and 1.6 (sensitivity 83.3%, specificity 66.7%), respectively.
Greater residual tumor thickness, based on MR imaging after the initial surgery, and a higher MIB-1 index are both important factors related to postoperative tumor regrowth in patients who have undergone incomplete VS resection. These patients require frequent neuroimaging investigation during follow-up to assure early detection of tumor regrowth.
Yukihiko Fujii, Ryuichi Tanaka, Shigekazu Takeuchi, Tetsuo Koike, Takashi Minakawa and Osamu Sasaki
✓ In order to evaluate the incidence and risk factors of hematoma enlargement in spontaneous intracerebral hemorrhage (ICH), 419 cases of ICH were reviewed. The first computerized tomography (CT) scan was performed within 24 hours of onset and the second within 24 hours of admission; a blood sample was taken for laboratory examination within 1 hour of admission. In 60 patients (14.3%) the second CT scan showed an enlarged hematoma. The incidence of enlargement significantly decreased with time (p < 0.05) and significantly increased with the severity of liver dysfunction and the volume of the hematoma on the first CT scan. Patients with an irregularly shaped hematoma had a higher risk of hematoma growth than those with a round hematoma. In addition, patients with hematoma enlargement were more likely to have coagulation abnormalities (low platelet counts and low levels of fibrinogen, α2-antiplasmin activity and platelet aggregation). Moreover, hematoma growth was associated with a poor clinical outcome.
It is concluded that patients admitted to a hospital within 6 hours of onset of ICH, especially those admitted within 2 hours, and patients with liver dysfunction or irregularly shaped large hematomas should be closely observed for at least 6 hours after onset in preparation for emergency surgery, since the risk of hematoma growth in these circumstances is high.
Toru Watanabe, Yoshiho Honda, Yukihiko Fujii, Miyako Koyama and Ryuichi Tanaka
Object. The purposes of this study were to evaluate the serial changes in diffusion anisotropy of the brain, probably reflecting axonal function in brain-dead patients, and thus to explore the possibility of quantitatively estimating the risk of brain death.
Methods. Ten patients suffering from stroke with or without impending brain death and 10 healthy volunteers were studied using three-dimensional anisotropy contrast (3DAC) magnetic resonance (MR) axonography with the aid of a 1.5-tesla MR imaging system. To detect changes in the diffusion anisotropy of neural bundles, the corticospinal tract was evaluated.
Diffusion anisotropy of short axonal fibers decreased immediately after apparent brain death. Whereas the trichromatic coefficients of the corticospinal tract greatly diminished between 6 and 12 hours after apparent brain death, the coefficients of the corpus callosum and the optic radiation decreased in less time, that is, between 1 and 6 hours. The coefficients of these three bundles turned isotropic between 24 and 44 hours after apparent brain death.
Conclusions. Results of 3DAC MR axonography revealed that diffusion anisotropy of neural bundles diminished between 1 and 12 hours after the onset of apparent brain death, probably depending on the length of the bundles, and disappeared between 24 and 44 hours after the onset of brain death, which might reflect dynamic changes of axonal structure and indirectly herald axonal dysfunction. These findings seem to be greatly helpful in establishing an appropriate method to estimate the risk of brain death quantitatively and in forming the basis of future definitions of brain death.