Spike-triggered fMRI in reading epilepsy: involvement of left frontal cortex working memory area

OBJECTIVE

To determine the origin of epileptiform activity in reading epilepsy (RE) and the association between these regions and regions activated by reading, and to assess brain morphometry in these areas.

METHODS

In two subjects with RE, EEG was recorded inside the three tesla MRI while subjects read silently. Spike-triggered fMRI images were compared to baseline. In a second fMRI study, 30 seconds of silent reading was compared to visual fixation. Morphometry of these areas was assessed using curvilinear surface reconstruction. Left central sulcal patterns in three subjects with RE were compared to three subjects with idiopathic generalized epilepsy (IGE) and 12 normal controls.

RESULTS

One subject with RE showed spike-related activity (17 spikes) in the left precentral gyrus, and bilaterally in the central sulcus and globus pallidus. The other showed no definite activation owing to low spike numbers (4 spikes). In both subjects, the block reading task recruited normal visual and language areas including the left posterior middle frontal gyrus. Two subjects with RE showed an unusual gyrus branching anteriorly off the left central sulcus. A similar sulcal pattern was seen in none of the subjects with IGE and only 1 of 12 controls.

CONCLUSION

Spike activity overlapped with reading activity in the left middle frontal gyrus, a structure recruited during working memory cognitive tasks. The authors postulate that, because of a local structural anomaly, the spikes of reading epilepsy spread from working memory areas into adjacent motor cortex, activating a cortical subcortical circuit.

Reemergence of activation with poststroke somatosensory recovery: a serial fMRI case study

The authors demonstrate the potential for poststroke return of activation in regions normally involved in touch discrimination in a serial, whole-brain fMRI study of a patient with marked sensory loss followed by good recovery. A return of activation in ipsilesional primary and bilateral secondary somatosensory cortices was observed at 3 months after stroke and was maintained at 6 months, indicating a reemergence of activation after the interval of somatosensory recovery. There was little evidence of neural plastic changes early after stroke (2 weeks), when sensory loss was severe.

Comparison of hippocampal volumetry at 1.5 tesla and at 3 tesla

PURPOSE

Hippocampal volumetry using magnetic resonance imaging (MRI) is a common clinical study in epilepsy patients. Most clinical MR scans operate at 1.5 tesla (T); however, there is increasing use of scanners of a higher field strength. We analyzed whether control data of hippocampal volumes can be used across different field-strength scanners.

METHODS

We studied eight adult healthy controls twice at both 1.5 and 3 T. Bilateral hippocampal volumes were measured by manual outlining. Measurement error was analyzed based on the variability between two measurements at the same field strength, and intrascanner variability was analyzed based on the difference between measurements obtained at 1.5 and at 3 T.

RESULTS

The measurement error was 4.0% (+/-3.1) at 1.5 T, and 3.4% (+/-2.5) at 3 T. The intrascanner variability between measurements at 1.5 and at 3 T was 6% (+/-3.9). The intrascanner variability was not different from the measurement error.

CONCLUSIONS

Control hippocampal volume measurements obtained at 1.5 and at 3 T were not different.

Hippocampal T(2) abnormalities correlate with antecedent events and help predict seizure intractability

INTRODUCTION

We performed hippocampal T(2) relaxometry as part of a routine magnetic resonance imaging (MRI) examination in 50 normal controls and 127 consecutive patients referred because of suspected seizures.

METHODS

On the basis of T(2) values in controls (100.2 +/- 4.2 ms) we defined normal as <110 ms (<mean + 2 SD), borderline as 110-113 ms (mean + 2 SD to mean + 3 SD) and abnormal as >113 ms (>mean + 3 SD).

RESULTS

After detailed investigation, 103 of these 127 patients had epilepsy and 24 did not. In the nonepilepsy group, none had abnormal hippocampal T(2) values. Twenty-seven of the 103 patients in the epilepsy group had abnormal values, 7 were borderline and 69 were normal. Only 5 patients with abnormal T(2) values did not have temporal lobe epilepsy: 1 had extratemporal lobe epilepsy, 1 had generalized epilepsy and 3 had unclassified epilepsy. Twenty-two of 27 (81%) patients with abnormal hippocampal T(2) values had intractable epilepsy [compared with 32 of 69 (46%) patients with normal values; p < 0.05, chi(2) test]. Two thirds of patients with abnormal values had a history of a major antecedent event (compared to only 7% of those with normal values, p < 0.05, chi(2) test).

CONCLUSION

Abnormal T(2) relaxometry is significantly associated with intractable epilepsy as well as with major antecedent events.

Experience with diffusion-weighted imaging in an acute stroke unit

We performed diffusion-weighted MRI (DWI) on a standard 1.5-tesla MRI scanner using a high-speed stimulated echo pulse sequence (turboSTEAM) in 9 stroke patients and 9 control subjects to investigate whether this technique can be used clinically to assist in ischaemic stroke diagnosis within the time frame for potential therapy. Stroke patients underwent DWI between 3.75 h and 3 days after stroke onset. Three patients were studied on more than one occasion. DWI was normal in the 9 controls. Seven of 9 stroke patients showed areas of increased signal on DWI. DWI detected cerebral ischaemia 3.75 h after stroke onset when both CT and T2-weighted MRI were normal. In 6 DWI-positive patients studied at later times, increased signal on T2-weighted images was present at the same time. Two patients had normal CT, T2-weighted and DWI images; both made good neurological recoveries. For the routine assessment of stroke patients, DWI implemented on a standard MRI system can provide additional information of clinical value to that obtained with conventional pulse sequences. In particular it facilitates early detection of cerebral ischaemia during the first few hours after stroke.