Assessment of the preferred plane and sequence in the depiction of mesial temporal sclerosis using magnetic resonance imaging

RATIONALE AND OBJECTIVES

Definition of optimal magnetic resonance (MR) scanning plane and conventional MR sequence for the detection of mesial temporal sclerosis (MTS).

METHODS

Coronal and axial T2-weighted images and axial T2-weighted images parallel to the long axis of the hippocampus (APLAH) and coronal inversion recovery (IR) images were obtained in patients with medically intractable temporal lobe epilepsy in their phase 1 preoperative evaluation. Thirty-three consecutive MR scans were reviewed by a panel of three radiologists. Twenty-three patients had MR abnormalities consistent with MTS, and ten scans were normal. To assess the best single scanning technique, another group of three radiologists, who were masked to all patient data, individually assessed the different planes and sequences of the 33 studies presented separately in a random fashion. For each plane and sequence, the likelihood (L) ratio for the correct diagnosis was determined separately.

RESULTS

For all planes considered separately, a likelihood ratio of 4.4 was optimal for the coronal T2-weighted images. The likelihood ratio of APLAH T2 was 2.2; of axial T2, 3.9; of coronal IR, indefinite because of 100% specificity.

CONCLUSIONS

For the assessment of MTS, coronal T2-weighted images were considered the best single scanning technique.

Cerebral metabolic differences between the severe and critical hypoperfused brain

Occlusion or severe stenosis, with a reduction in the diameter of the extracranial arteries of more than 70%, may lead to hypoperfusion of the brain with an increased risk of cerebral infarction. The aim of this study was to investigate whether a decrease in metabolism in noninfarcted hypoperfused cerebral areas is correlated with the level of hypoperfusion. Fifty-one patients without infarcts, with borderzone infarcts, with territory infarcts, and fourteen healthy control subjects were investigated with MRI and MR spectroscopic imaging. The NAA/choline ratio in the symptomatic hermisphere was significantly decreased in patients with borderzone infarcts compared with patients without infarcts, with patients with territory infarcts, and with control subjects. Furthermore, patients with borderzone infarcts had a relatively high frequency of cerebral lactate. These results indicate that there might be a lower limit of hypoperfusion that can be measured indirectly with MR spectroscopic imaging, below which irreversible cerebral damage occurs.

Familial subarachnoid hemorrhage: distinctive features and patterns of inheritance

To delineate the distinctive features of familial subarachnoid hemorrhage, we compared gender and age at the time of subarachnoid hemorrhage, as well as site and number of aneurysms, in patients with familial subarachnoid hemorrhage (at least 1 first-degree relative with subarachnoid hemorrhage) and patients with sporadic subarachnoid hemorrhage (no subarachnoid hemorrhage in first- or second-degree relatives), in a prospective, hospital-based series of patients. In addition we studied the pattern of inheritance in 17 families with familial subarachnoid hemorrhage. Mean age at the time of hemorrhage in patients with the familial form was 6.8 years lower than that in those with the sporadic form, and middle cerebral artery aneurysms occurred more often in patients with familial disease. Sex distribution and number of aneurysms were similar in the two groups. Inheritance was compatible with autosomal dominant transmission in some families, and with autosomal recessive or multifactorial transmission in others. In our 5 families as well as in all 18 previously reported families with two affected generations, the age at the time of subarachnoid hemorrhage was invariably lower in later generations, which is suggestive of anticipation. We conclude that familial subarachnoid hemorrhage is a separate entity with occurrence at a young age, predilection for aneurysms of the middle cerebral artery, and variable modes of inheritance, including autosomal dominant inheritance with possible anticipation.

Temporal lobe epilepsy: the various MR appearances of histologically proven mesial temporal sclerosis

PURPOSE

To determine the frequency of appearance of various MR signs in mesial temporal sclerosis, to determine the optimal scanning planes for their visualization, and to propose a histologic explanation for the diminished demarcation between gray and white matter in the temporal lobe, a frequent MR finding in patients with mesial temporal sclerosis.

METHODS

MR scans of 14 surgically treated patients with epilepsy and histologically proven mesial temporal sclerosis were assessed for the presence of six features: feature 1, high signal intensity in the hippocampus; 2, reduced hippocampal size; 3, ipsilateral atrophy of the hippocampal collateral white matter; 4, enlarged temporal horn; 5, reduced gray-white matter demarcation in the temporal lobe; and 6, decreased temporal lobe size.

RESULTS

Feature 1 was present in 14 patients and was best appreciated on the T2-weighted images in planes parallel to the long axes of the hippocampi. Feature 2, present in 12 patients, and feature 6, present in 9 patients, were optimally seen in the coronal planes and on the inversion-recovery sequences in particular. Feature 3, present in 12 patients, was optimally seen on the coronal T2-weighted images. Feature 4, seen in 11 patients, was equally well seen in all planes (transverse, coronal, and parallel to the long axes of the hippocampi). Feature 5, seen in 10 patients, was best appreciated on the T2-weighted images in the planes of the long axes of the hippocampi. Histologic investigation of the temporal lobe white matter in the 10 patients with feature 5 demonstrated on the MR scan showed abnormalities in 7 cases. Oligodendroglia cell clusters were found in 6, with concomitant corpora amylacea in 1 case and perivascular macrophages with pigment a sole finding in another case.

CONCLUSION

Of the six features found in cases of mesial temporal sclerosis on MR, increased hippocampal signal intensity is the most consistent. A decreased gray-white matter demarcation in the temporal lobe parenchyma is also a frequent feature of this disease. A combination of multiple scanning planes results in an optimal demonstration of lesions.

Visually induced central pain and arm withdrawal after right parietal lobe infarction

A 46 year old man with ischaemic infarction of the right parietal cortex had left hemianaesthesia when his eyes were closed. With eyes open, visual stimuli induced withdrawal of the arm and a burning pain in the numb side of the body. Visually induced central pain is a new clinical finding and may be related to damage of cells with anticipatory inhibitory function in the parietal association cortex.

Segmental fasciculations as a late sequel of spinal cord injury

In two patients with a history of spinal cord injury many years ago fasciculations developed in muscles belonging to previously damaged segments. In both patients MRI of the cervical spine showed an area of abnormal signal intensity representing a cavity, near the level of the neurological abnormalities and the cord injury. During a 4-year follow-up period no new neurological or MRI abnormalities were detected. A hypothesis for the genesis of fasciculations following spinal cord injury is presented.

Impact of microembolism and hemodynamic changes in the brain during carotid endarterectomy

BACKGROUND AND PURPOSE

Monitoring of carotid endarterectomy with electroencephalography and transcranial Doppler ultrasonography provides instantaneous information about hemodynamic changes and embolic signals. However, a relation between these findings and intraoperative infarcts has not yet been demonstrated.

METHODS

In this study we compared preoperative and post-operative computed tomographic scans (58 patients) or magnetic resonance imaging (40 patients) of the brain, assessed by two independent observers, to detect intraoperative infarcts, and we related any such new lesions to the findings of intraoperative monitoring.

RESULTS

In the computed tomography series one intraoperative infarct occurred, with corresponding clinical deficits. In the magnetic resonance group four patients developed new lesions that occurred intraoperatively, all of which were clinically silent. There was a significant relation between the number of embolic signals during the surgical dissection of the carotid artery and the occurrence of intraoperative infarcts (P < .005). Three of the four infarcts were of the lacunar type; the fourth patient had a border-zone infarct, associated not only with many embolic signals but also with low flow during cross-clamping. There were no demonstrable ultrasound side effects on brain tissue.

CONCLUSIONS

Embolic signals detected by transcranial Doppler monitoring in the dissection phase of carotid endarterectomy show a significant relation to new ischemic lesions and therefore are potentially harmful. The phenomenon should alert the vascular surgeon.

Retinoblastoma: CT and MRI

To evaluate the effectiveness of CT and MRI at 0.5 T in the diagnosis and staging of retinoblastoma, we studied 11 patients in whom retinoblastoma was clinically suspected. Nine of the eleven had surgically proven retinoblastoma; in the other two a diagnosis of Coats' disease was made. MRI was not as specific as CT for diagnosing retinoblastoma, due to its lack of sensitivity in detecting calcification; it did, however, have superior contrast resolution. On MRI, Coats' disease was reliably diagnosed and easily differentiated from retinoblastoma. Moreover, the greater ability of MRI to differentiate subretinal fluid from tumour also confers high accuracy in measuring tumour size. CT is still the study of choice in the diagnosis of retinoblastoma, but when MRI is available, it should be performed for better differentiation from lesions such as Coats' disease.

Simulation of susceptibility artifacts in 2D and 3D Fourier transform spin-echo and gradient-echo magnetic resonance imaging

A method is presented for simulating susceptibility artifacts in 2D and 3D spin-echo and gradient-echo imaging of arbitrary susceptibility distributions. The method incorporates object induced field perturbations in the time domain (k-space) and is demonstrated for spherical nonuniformities in susceptibility. Both simulations and experimental results for multi-slice 2D and 3D imaging of phantoms and human subjects are provided.

Carotid bifurcation imaging: magnetic resonance angiography compared to conventional angiography and Doppler ultrasound

PURPOSE

to evaluate the clinical usefulness of the two dimensional "Time of Flight" (2D TOF) Magnetic Resonance Angiography technique (MRA) in imaging the carotid bifurcation as compared to conventional angiography and pulsed and colour Doppler ultrasound.

METHODS

in 19 patients with possible cerebrovascular disease and eight volunteers, contrast angiography was compared with MRA in 21 carotid bifurcations and with Doppler ultrasound in 23 bifurcations by two independent observers. In 19 bifurcations, all three techniques were available for comparison. Internal carotid arteries were graded normal/minimal disease, mild, moderate or severe stenosis, or occluded.

RESULTS

overall agreement between contrast angiography and MRA existed in 62% for one observer and 76% for the other. When MRA and Doppler agreed, agreement between these two investigations and contrast angiography existed in 77-81%. The major problem with MRA was overestimation of moderately stenosed vessels; 50% of the vessels with a moderate stenosis on contrast angiography were judged severely stenosed on MRA. An occlusion was never mistaken for a stenosis by MRA. Evaluating the separate slices, acquired in the 2D TOF MRA investigation, appeared to be essential to avoid this mistake.

CONCLUSION

at present 2D TOF MRA is not clinically useful for diagnosing the degree of carotid artery stenosis. MRA has a clear tendency to overestimate the degree of stenosis especially moderately severe stenoses. To date, there are no objective methods to correct for this mistake. Technical improvements may make MRA a better diagnostic tool in the future.

Recurrent brain abscess due to an unexpected foreign body

We report an exceptional case of a patient with chronic frontal sinusitis complicated by chronic osteomyelitis and a cutaneous fistula. A recurrent brain abscess developed and was only cured after a very unusual wooden retained foreign body was removed at surgery. The hazards of wood as a foreign body are discussed and it is stressed that the possibility of a retained foreign body, even unsuspected, must always be borne in mind.

Hypertension in the elderly is associated with white matter lesions and cognitive decline

Forty-two elderly patients (mean age, 66.2 +/- 5.1 yr) with hypertension, treated for an average of 17.3 years (standard deviation, 10.3), and 42 control subjects (mean age, 66.5 +/- 4.8 yr), matched for age, sex, and level of education, were studied with regard to the detection of lesions in the cerebral white matter with magnetic resonance imaging (MRI), particularly with axial T2-weighted images. The assessment of the MRI scans was blinded. Ten hypertensive patients showed confluent lesions in the white matter, versus only 1 control subject (Chi-square test, p = 0.01). The presence of diffuse lesions of the white matter was related to age but not to the known duration of hypertension, nor to the presence of any other cardiovascular risk factors. Cognitive function was measured in 34 hypertensive patients and in 18 control subjects. Results of the Mini-Mental State Examination, the Stroop color-word test, Trailmaking test, and the visual subtest of the Wechsler Memory Scale were worse in patients with confluent lesions of the white matter; there was no difference in mental functioning between hypertensive patients and control subjects with normal white matter or with only small focal lesions. Our findings suggest that long-standing hypertension in some patients may cause not only strokes but also chronic end-organ damage of the brain in the form of demyelination of the white matter, with cognitive decline.

[Balloon embolization of a large carotid-cavernous fistula]

A 58-year-old male patient with a giant carotid-cavernous fistula was treated by means of endovascular balloon embolisation. The fistula was closed, and good antegrade flow in the carotid artery and intracranial vessels was obtained. Based on this case history, the pathophysiology, ultrasonographic and angiographic evaluation and treatment options are reviewed.

Nonaneurysmal perimesencephalic subarachnoid hemorrhage: CT and MR patterns that differ from aneurysmal rupture

We describe a characteristic distribution of cisternal blood in 52 patients with nonaneurysmal subarachnoid hemorrhage proved by a normal angiogram. On CT, the center of the bleeding was located immediately anterior to the brainstem in all patients, which was confirmed in four patients who were studied with MR imaging. Extension to the ambient cisterns or to the basal parts of the sylvian fissures was common, but the lateral sylvian or anterior interhemispheric fissures were never completely filled with blood. Rupture into the ventricular system did not occur. MR demonstrated downward extension of the blood anterior to the brainstem as far as the medulla, but failed to detect the source of hemorrhage. Our aim was to determine whether this so-called nonaneurysmal perimesencephalic hemorrhage could be distinguished from aneurysmal subarachnoid hemorrhage on early CT scans. Two neuroradiologists were shown a consecutive series of 221 CT scans of patients with subarachnoid hemorrhage who subsequently underwent angiography. Only one patient with a basilar artery aneurysm on angiography was incorrectly labeled by both observers as having a nonaneurysmal perimesencephalic pattern of hemorrhage. The high predictive value of the perimesencephalic pattern of hemorrhage for a normal angiogram (0.95 and 0.94, respectively, for the two observers) and the excellent interobserver agreement (kappa 0.87) demonstrate that nonaneurysmal perimesencephalic hemorrhage can be distinguished on CT in the majority of patients. Recognition of this pattern of hemorrhage is important as patients with this subset of subarachnoid hemorrhage have an excellent prognosis.

Development of multifocal haemorrhage in a cerebral infarct during computed tomography

Images

Cranial nerve palsy as a delayed complication of attempted infanticide by insertion of a stylet through the fontanel. Case report

A child suffered a sixth and seventh cranial nerve palsy due to intracerebral insertion of a stylet. The stylet was introduced through the anterior fontanel, most probably in an attempt at infanticide. The migration of the stylet through the brain was monitored because the child was first examined 6 years earlier. At operation the cranial part of the stylet lay in the fourth ventricle, compressing the facial nerve as well as the nucleus of the abducens nerve. The lower part of the stylet had reached the C-5 level.

Progression of acute hydrocephalus in subarachnoid haemorrhage: a case report documented by serial CT scanning

A patient with a perimesencephalic subarachnoid haemorrhage gradually developed, within the first day, progressively impaired consciousness, small non-reactive pupils, and defective upward gaze. Three successive CT scans showed progressive enlargement of the lateral and third ventricles. Ventricular shunting resulted in complete recovery.

The role of computed tomography in patients with lacunar stroke in the carotid territory

In a prospective study of 78 patients presenting with recent clinical features of a supratentorially located lacunar infarct (LI), serial CT-scanning with contiguous 6, 5 or 3 mm slices was carried out. LI was found in 59 patients (76%; 95% confidence limits 65-85%). Lesions other than lacunar infarcts were found in 5 patients (6%; 95% confidence limits 2-14%); in only 14 patients could no abnormalities be detected (18%; 95% confidence limits 10-28%). There was no relationship between the detection rate on CT on the one hand and the type of lacunar syndrome, the number of previous TIA's, and the duration or severity of the neurological deficit on the other. A new protocol of CT-scanning for screening LI is advocated for situations where no MRI facilities are available or no patient cooperation can be obtained.

Ischaemic stroke in the basal ganglia and internal capsule in childhood

Ischaemic stroke in childhood is rare. In particular, there have only been a few reports of lacunar infarcts in children. In this study, four children with true lacunar infarcts and four with larger subcortical infarcts are described. We compare the clinical features and the possible pathogenesis of ischaemic strokes in the basal ganglia and internal capsule in childhood with those in adults, and discuss diagnostic and therapeutic management.

Carotid angiography in patients with lacunar infarction. A prospective study

We prospectively studied the results of carotid angiography in 45 patients with transient or nondisabling neurologic deficits caused by lacunar infarction in the internal capsule or corona radiata and demonstrated by computed tomography. An ipsilateral stenosis at the bifurcation of the internal carotid artery was found in 14 patients (31%, 95% confidence limits 18-47%), seven of whom also had stenosis of the contralateral internal carotid artery. In previous studies an average of 65% of patients with transient hemispheric deficit had internal carotid artery stenosis or occlusion. Hypertension and hypertensive retinal vasculopathy assessed by fundus photographs were found in most patients, but not significantly more often in the patients without internal carotid artery stenosis. Our findings support the notion that small vessel disease rather than emboli from the carotid bifurcation is the most common cause of lacunar infarction.