Thalamic Diaschisis in Acute Ischemic Stroke: Occurrence, Perfusion Characteristics, and Impact on Outcome.

BACKGROUND AND PURPOSE: Ipsilateral thalamic diaschisis (ITD) describes the reduction of thalamic function, metabolism, and perfusion resulting from a distant lesion of the ipsilateral hemisphere. Our aim was to evaluate the perfusion characteristics and clinical impact of ITD in acute middle cerebral artery stroke, which does not directly affect the thalamus. METHODS: One hundred twenty-four patients with middle cerebral artery infarction were selected from a prospectively acquired cohort of 1644 patients who underwent multiparametric computed tomography (CT), including CT perfusion for suspected stroke. Two blinded readers evaluated the occurrence of ITD, defined as ipsilateral thalamic hypoperfusion present on ≥2 CT perfusion maps. Perfusion alterations were defined according to the Alberta Stroke Program Early CT Score regions. Final infarction volume and subacute complications were assessed on follow-up imaging. Clinical outcome was quantified using the modified Rankin Scale. Multivariable linear and ordinal logistic regression analysis were applied to identify independent associations. RESULTS: ITD was present in 25/124 subjects (20.2%, ITD+). In ITD+ subjects, perfusion of the caudate nucleus, internal capsule, and lentiform nucleus was more frequently affected than in ITD- patients (each with P<0.001). In the ITD+ group, larger cerebral blood flow (P=0.002) and cerebral blood volume (P<0.001) deficit volumes, as well as smaller cerebral blood flow-cerebral blood volume mismatch (P=0.021) were observed. There was no independent association of ITD with final infarction volume or clinical outcome at discharge in treatment subgroups (each with P>0.05). ITD had no influence on the development of subacute stroke complications. CONCLUSIONS: ITD in the form of thalamic hypoperfusion is a frequent CT perfusion finding in the acute phase in middle cerebral artery stroke patients with marked involvement of subcortical areas. ITD does not result in thalamic infarction and had no independent impact on patient outcome. Notably, ITD was misclassified as part of the ischemic core by automated software, which might affect patient selection in CT perfusion-based trials.

The Posterior Limb of the Internal Capsule as the Subcortical Transitional Zone of the Anterior and Posterior Circulations: Insights from Human 7T MRI.

BACKGROUND: In patients with cerebral infarction, identifying the distribution of infarction and the relevant artery is essential for ascertaining the underlying vascular pathophysiological mechanisms and preventing subsequent stroke. However, visualization of the basal perforating arteries (BPAs) has had limited success, and simultaneous viewing of background anatomical structures has only rarely been attempted in living human brains. Our study aimed at identifying the BPAs with 7T MRI and evaluating their distribution in the subcortical structures, thereby showing the clinical significance of the technique. METHODS: Twenty healthy subjects and 1 patient with cerebral infarction involving the posterior limb of the internal capsule (ICpost) and thalamus underwent 3-dimensional fast spoiled gradient-echo sequence as time-of-flight magnetic resonance angiography (MRA) at 7T with a submillimeter resolution. The MRA was modified to detect inflow signals from BPAs, while preserving the background anatomical signals. BPA stems and branches in the subcortical structures and their origins were identified on images, using partial maximum intensity projection in 3 dimensions. RESULTS: A branch of the left posterior cerebral artery (PCA) in the patient ran through both the infarcted thalamus and ICpost and was clearly the relevant artery. In 40 intact hemispheres in healthy subjects, 571 stems and 1,421 branches of BPAs were detected in the subcortical structures. No significant differences in the numbers of stems and branches were observed between the intact hemispheres. The numbers deviated even less across subjects. The distribution analysis showed that the subcortical structures of the telencephalon, such as the caudate nucleus, anterior limb of the internal capsule, and lenticular nucleus, were predominantly supplied by BPAs from the anterior circulation. In contrast, the thalamus, belonging to the diencephalon, was mostly fed by BPAs from the posterior circulation. However, compared with other subcortical structures, the ICpost, which marks the anatomical boundary between the telencephalon and the diencephalon, was supplied by BPAs with significantly more diverse origins. These BPAs originated from the internal carotid artery (23.1%), middle cerebral artery (38.5%), PCA (17.3%), and the posterior communicating artery (21.1%). CONCLUSIONS: The modified MRI method allowed the detection of the relevant BPA within the infarcted area in the stroke survivor as well as the BPAs in the subcortical structures of living human brains. Based on in vivo BPA distribution analyses, the ICpost is the transitional zone of the anterior and posterior cerebral circulations.

Brain MRI findings in patients with Fabry disease.

BACKGROUND: To evaluate the presence of ischemic and hemorrhagic lesions in brain MRI of patients with Fabry disease (FD). METHODS: Brain MRI studies in 46 consecutive patients were evaluated using classic sequences as well as GRE-weighted images, for ischemic lesions and chronic microbleed detection. Of the 36 adult patients (15 males, mean age 31.2 years; 21 females, mean age 41.6 years). All had signs or symptoms of FD but lacked history of stroke or TIA. RESULTS: Ten patients under 20 years of age initially presented a normal MRI. One child developed a hyperintense occipital lesion on T2-weighted imaging during control MRI. Sixteen adult patients (44.4%) had brain MRI evidence of small vessel disease in the basal ganglia, corona radiata, thalamus or brainstem, as well as in the periventricular white matter. Patients with MRI abnormalities were older (45.6 vs 30.9 years, p=0.005), with more vascular risk factors (1.2 vs 0.6 p=0.043). Three women (mean age 59.5 years) presented deep chronic microbleeds identified by GRE. Moreover, Flair and T2-weighted images revealed white matter disease and deep gray matter involvement. CONCLUSION: 44.4% of adult patients with FD without clinical history of CVA or prior dialysis had evidence of small vessel disease on MRI and 11% showed cerebral microbleeds. FD is a treatable disorder that should be routinely included in the differential diagnosis of ischemic and microhemorrhagic lesions in young adults.

Lacunar stroke attributable to radiation-induced intracranial arteriopathy.

We report the rare presentation of lacunar stroke syndrome secondary to single perforator mouth occlusion from radiation-induced middle cerebral artery (MCA) stem arteriopathy. A 30-year-old female had acute-onset right-sided ataxic hemiparesis and dysarthria. As a child, she had a medulloblastoma of the posterior fossa and had surgery followed by cranial radiotherapy. She had no significant vascular risk factors. Acute CT showed extensive bilateral basal ganglia and left thalamic calcification; DWI showed a left internal capsule lacunar infarct; and MRA and CTA showed a 50% stenosis of the proximal left MCA.

Radiosurgery for basal ganglia, internal capsule, and thalamus arteriovenous malformation: clinical outcome.

OBJECTIVE: Radiosurgery is accepted as the first option for treating deep arteriovenous malformations (AVMs), although the clinical outcome in this subgroup of brain AVMs is not well studied. The objective of this study is to review our experience with radiosurgical treatment for these AVMs. METHODS: Between October 1989 and December 2000, 45 patients with deep AVMs (including basal ganglia, internal capsule, and thalamus) underwent stereotactic radiosurgery. Three patients were lost to follow-up and therefore were excluded from this study. Patient characteristics and outcomes were collected and analyzed. The obliteration prediction index and the radiosurgery-based AVM score were calculated and tested. RESULTS: Forty-two patients were followed up for a median of 39 months (range, 25-90 mo; mean, 45.8 mo). The median maximum AVM diameter during the radiosurgery was 1.8 cm (range, 0.9-4.0 cm; mean, 2.07 cm), and the median AVM volume was 2.8 cm(3) (range, 0.2-18.3 cm(3); mean, 4.74 cm(3)). The mean marginal dose was 16.2 Gy (median, 15 Gy), and the median maximum dose was 22.4 Gy (range, 16.6-30 Gy). The AVM cure rate after the first radiosurgical treatment, using angiography- and magnetic resonance imaging-confirmed obliteration, was 61.9%. The predicted obliteration using the obliteration prediction index was 60%. Eight patients developed radiation-induced complications (19%). The deficit was transient in three patients (7.1%) and permanent in five patients (11.9%). The risk of postradiosurgical hemorrhage in this cohort was 9.5% for the first year, 4.7% for the second year, and 0% thereafter. Excellent outcome (obliteration plus no new deficit) was achieved in 70% of the patients in the group with radiosurgery-based AVM score less than 1.5 compared with 40.9% in the group with radiosurgery-based AVM score greater than 1.5% (P = 0.059). CONCLUSION: Radiosurgery for deep AVMs has a satisfactory obliteration rate and acceptable morbidity, considering the risk of hemorrhage without treatment and the risk of morbidity associated with other treatment modalities.

Prediction of neurologic deterioration in patients with lacunar infarction in the territory of the lenticulostriate artery using perfusion CT.

BACKGROUND AND PURPOSE: A significant proportion of patients with lacunar infarctions experience neurologic deterioration after onset. However, no clinical examination has been established for prediction of the progress of symptoms. To determine the hemodynamic predictors of such progression, we performed perfusion CT to quantitatively assess cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT) of patients with lacunar infarctions in the territory of the lenticulostriate artery. METHODS: We performed MR imaging and perfusion CT of 26 patients with lacunar infarction within 24 hr after onset. On the CBF map on perfusion CT scans, a round small region of interest was set at the region, with decreased CBF in the territory of the lenticulostriate artery (region of interest 1). Another region of interest was set in the mirror position to region of interest 1 in the contralateral hemisphere (region of interest 2). Using these two regions of interest, CBF, CBV, and MTT were measured. All patients underwent neurologic and MR imaging follow-up while receiving equivalent medical treatment. RESULTS: Neurologic deterioration after onset was shown in 13 patients (progress group), whereas no neurologic deterioration was shown in the other 13 patients (control group). In the progress group, lacunar infarctions were enlarged on follow-up MR images. The ratio of region of interest 1/region of interest 2 showed significantly lower CBF and higher MTT in the progress group than in the control group. CONCLUSIONS: These results suggest that progressive lacunar infarction in the territory of the lenticulostriate artery could be predicted with a higher MTT ratio (>1.26) and a lower CBF ratio (<0.76) on perfusion CT scans obtained within 24 hr after onset.

Transcranial motor evoked potentials during basilar artery aneurysm surgery: technique application for 30 consecutive patients.

OBJECTIVE: Microsurgical clipping of basilar artery aneurysms carries a risk of neurological compromise resulting from midbrain or thalamic ischemia. Somatosensory evoked potential (SSEP) monitoring and electroencephalography are the standard techniques for assessing the level of cerebroprotective anesthesia and monitoring ischemia during temporary occlusion or after permanent clipping. Transcranial motor evoked potential (TcMEP) monitoring was added to determine whether this modality improved intraoperative monitoring. METHODS: Combined SSEP/electroencephalographic/TcMEP monitoring was used for 30 consecutive patients with basilar artery apex aneurysms in the past 1.5 years. Voltage thresholds were recorded before, during, and after aneurysm treatment for the last 10 patients. RESULTS: All 30 patients underwent an orbitozygomatic craniotomy for clipping (28 patients), wrapping (1 patient), or superficial temporal artery-superior cerebellar artery bypass (1 patient). Electrophysiological changes occurred for 10 patients (33%), elicited by temporary clipping (6 patients), permanent clipping (3 patients), or retraction (1 patient). Isolated SSEP changes were observed for one patient, isolated TcMEP changes for five patients, and changes in both TcMEPs and SSEPs for four patients. Among patients with simultaneous changes, TcMEP abnormalities were more robust and occurred earlier than SSEP abnormalities. Impaired motor conduction was detected first with an increase in the voltage threshold (from 206 +/- 22 to 410 +/- 49 V, P < 0.05, n = 3) and then with loss of TcMEP responses. SSEP and TcMEP signals returned to baseline values for all patients after corrective measures were taken. CONCLUSION: TcMEP monitoring can be safely and easily added to traditional neurophysiological monitoring during basilar artery aneurysm surgery. These results suggest that TcMEPs may be more sensitive than SSEPs to basilar artery and perforating artery ischemia. This additional intraoperative information might minimize the incidence of ischemic complications attributable to prolonged temporary occlusion or inadvertent perforator occlusion.

Regional cerebral blood flow and magnetic resonance spectroscopic imaging findings in diaschisis from stroke.

BACKGROUND AND PURPOSE: This study evaluated blood flow and metabolite changes in cerebral diaschisis from internal capsule region infarction using regional cerebral blood flow (rCBF) single-photon emission computed tomography (SPECT) and 1H magnetic resonance spectroscopic imaging (MRSI). We hypothesized that complementary measures of diaschisis effects in white matter (characterized by 1H MRSI) and gray matter (characterized by changes in rCBF) can be measured and exhibit parallel changes. METHODS: Five stroke patients and 16 normal controls underwent Tc-99m hexamethylpropyleneamine-oxime brain SPECT and 1H MRSI at 4.1 T. The metabolites N-acetyl aspartate (NAA) and creatine (Cr) were measured using 1H MRSI. The tissue content was expressed as the percent of gray or white matter in each MRSI voxel to allow comparison of the differential effects of diaschisis in gray and white matter tissue types. The blood flow and metabolite changes were evaluated at superior cerebral regions distant from the stroke to allow a measure of diaschisis relatively unconfounded by their expected changes in the infarction region. RESULTS: The rCBF SPECT data in stroke patients showed a perfusion defect, with size ranging from 1.23 cc to 10.23 cc, in the region of cortical diaschisis. 1H MRSI showed increased Cr/NAA ratios in regions of white matter diaschisis. There was a tendency for larger rCBF defect size to be associated with greater increases in Cr/NAA values in the same diaschitic cerebral hemisphere, ipsilateral to the infarction. CONCLUSION: Diaschisis ipsilateral to stroke in white matter can be characterized by 1H MRSI, and diaschisis ipsilateral to stroke in cortical gray matter regions can be characterized by changes in rCBF. The tendency for greater reductions in cortical rCBF values to be associated with increased Cr/NAA values in the same diaschitic cerebral hemisphere implies that a relationship exists between rCBF reductions in gray matter and abnormal changes in white matter subservient to it.

Clinical lacunar syndromes as predictors of lacunar infarcts. A comparison of acute clinical lacunar syndromes and findings on diffusion-weighted MRI.

OBJECTIVES: To evaluate if patients with acute lacunar syndromes have acute lacunar infarcts or other types of cerebral lesions on diffusion-weighted MRI. METHODS: Patients with acute lacunar syndromes underwent echo-planar diffusion MRI of the brain within 3 days after stroke onset. Localization and size of lesions with hyperintense signal were determined, compared with clinical characteristics and with findings on follow-up T2-weighted MRI. RESULTS: Twenty-three patients participated in the study. Thirteen patients had pure motor stroke, 1 pure sensory stroke, 8 sensorimotor stroke, and 1 ataxic hemiparesis. Twenty-two patients had at least one lesion with increased signal on diffusion-weighted MR images. These acute lesions were in the internal capsule/ basal ganglia/thalamus in 13 patients, subcortical white matter in 5 patients, brainstem in 2 patients, cortex (multiple small lesions) in 1 patient, and cortex + basal ganglia in 1 patient. The median volume of the lesions was 0.6 ml on the initial examination and on follow-up, of 17 patients after 1 to 5 months, 0.5 ml. CONCLUSIONS: Almost all patients with acute ischemic lacunar syndromes have acute lesions on echo-planar diffusion-weighted MRI within 3 days after stroke onset. These lesions are mostly small and subcortical, compatible with lacunar infarcts caused by single penetrating artery occlusion, but in a minor proportion of patients (2 of 23 in our study) a cortical involvement is found.

[A case of abulia without memory disturbance due to infarction of the bilateral genua of the internal capsules].

A 68-year-old right handed man with treated hypertension presented with acute-onset somnolence without hemiparesis, dysarthria or sensory disturbance. Although he became laconic and his verbal responses were only in short terms, his replies were accurate and judgmental. A cranial MRI in axial, coronal, and sagittal section revealed small hemorrhagic infarcts essentially limited to the bilateral capsular genua without involvement of the inferior thalamic peduncles. A 123I-IMP single photon emission CT disclosed remarkable hypoperfusion in the bilateral frontal cortex. After a week of somnolence, he gradually became wakeful, but was still abulic. Neuropsychological examinations revealed no memory disturbance. We consider that disconnection of the thalamo-frontal projection at the genua of the internal capsules caused somnolence, apathy, and abulia in our case. The hitherto reported cases of the genu infarcts that showed memory disturbance had the lesion involving both the inferior thalamic peduncle and its nearby mamillothalamic tract. In contrast, our case without memory disturbance had infarcts confined to the genua apparently sparing the two tracts, implicating that memory function may be preserved when such structures are intact.