Paramedian thalamic and midbrain infarct: clinical and neuropathological study

Tremor due to stroke

We report on four patients with unilateral tremor stemming from cerebrovascular accidents. In two patients with proven lesions of the thalamus, the tremor was irregular and, in addition, there was dystonic posturing of the affected arm. Tremor and dystonic posturing had appeared after the stroke. In the other two patients tremor had occurred immediately at the onset of the stroke and lasted only a few days. The tremors were of small amplitude and high frequency, and lesions could not be found on CT or MRI in these two patients. None of our patients showed signs of the so-called rubral tremor.

Infantile panthalamic infarct with a striking sonographic finding: the "bright thalamus"

A "bright thalamus" is not uncommonly observed in cranial sonograms of asphyxiated neonates, but not those of older infants. Three infants, aged 9-14 months, developed acute onset of seizures and disturbance of consciousness after a minor prodromal illness. Bilateral thalamic infarcts were demonstrated by ultrasonography and CT. One patient expired from causes not directly related to the infarcts; the other two survived with severe neurological sequelae.

Disruption of sleep-wake rhythmicity and daytime sleepiness in myotonic dystrophy

Ten patients with myotonic dystrophy (MyD) and excessive daytime sleepiness (EDS) were studied. Daytime sleepiness was assessed by means of a subjective alertness rating scale, multiple sleep latency tests and auditory event-related potentials. In addition, the diurnal pattern of daytime sleepiness and ultradian rhythm characteristics of nocturnal sleep were assessed. The multiple sleep latency tests and the P300 component of the auditory event-related potentials gave evidence of EDS, whereas the subjective alertness ratings did not. However, the alertness ratings showed a significantly reduced circadian periodicity as compared with controls. Consistent with this, no time-of-day effect was observed for the multiple sleep latency test outcomes. The ultradian rhythm characteristics of nocturnal sleep indicated a prolonged mean cycle duration and decreased stability of NREM/REM cycle. Moreover, the temporal structure of REM sleep showed a pattern similar to that of subjects who develop free-running rhythms when living in temporal isolation. These findings suggest that EDS in MyD reflects a complex and wide-spread malfunction of the circadian and ultradian timing system.

Iontophoretic effects of sigma ligands on rubral neurons in the rat

Iontophoretic application of the sigma ligands, 1,3-di-o-tolylguanidine (DTG), dextrallorphan, and (+)-pentazocine reliably inhibited the firing rate of rubral neurons. Dextrallorphan inhibited 87% of the neurons tested, DTG inhibited 76%, and (+)-pentazocine inhibited 50%. These inhibitions were current dependent and occurred without significant changes in spike amplitude or duration, suggesting that local anesthetic effects were not involved. In contrast to the other sigma ligands, iontophoretic application of (+)-3-PPP in the rat red nucleus resulted in very few inhibitions and tended to elicit weak excitations instead. Only 14% of rubral neurons were inhibited by (+)-3PPP, while 36% were excited. Although unusual, (+)-3-PPP has atypical effects when compared to other sigma ligands in numerous functional assays for sigma receptor activity. (+)-3-PPP, therefore, appears to have complex effects and may act through nonsigma mechanisms or through a different type of sigma binding site than the other compounds. The inhibition of firing rate produced by the more typical sigma ligands may contribute to the postural changes produced by microinjection of sigma ligands into the rat red nucleus.

Paramedian thalamopeduncular infarction: clinical syndromes and magnetic resonance imaging

We prospectively examined 11 patients with magnetic resonance imaging-documented infarction in the paramedian thalamopeduncular region, which is supplied by the superior mesencephalic and posterior thalamosubthalamic arteries. Variations in the size and rostral-caudal extent of infarction correlated with the following three clinical patterns: (1) With unilateral paramedian mesencephalic infarction, an ipsilateral third nerve paresis was accompanied by mild contralateral hemiparesis or hemiataxia. Contralateral ptosis and impaired upgaze were observed in two patients; one of them showed additional damage to the posterior commissure. (2) With bilateral infarction in the thalamopeduncular junction, involving the mesencephalic reticular formation, supranuclear vertical gaze defects were accompanied by impaired consciousness or memory, and mild aphasia in some patients. Persistent amnesia was observed only when the dominant anterior nucleus or mamillothalamic tract was damaged. (3) With larger thalamopeduncular infarcts, partial or complete third nerve paresis was combined with supranuclear gaze disturbance and delayed contralateral tremor. An unusual gaze disorder, a variant of the vertical "one-and-a-half syndrome," occurred with a small strategically placed lesion at the thalamopeduncular junction, best explained by selective damage to supranuclear pathways or partial nuclear involvement. The primary cause of these infarctions was embolism to the basilar apex or local atheroma at the origin of the posterior cerebral artery.

Thalamic amnesia: Korsakoff syndrome due to left thalamic infarction

In order to support the concept that a lesion of the thalamus is sufficient to cause a Korsakoff syndrome, we are presenting 5 patients, all of whom developed the syndrome after sustaining a left (dominant) thalamic infarction. Two patients had pure thalamic strokes followed by a permanent Korsakoff syndrome. One of these patients was studied with neuropsychometric testing, as well as with a modern MRI scan. In 2 other patients, clinical and imaging data indicate that infarction was not limited to the thalamus. Another patient had bilateral thalamic infarcts but only a temporary Korsakoff syndrome. Neuropathological data are needed to elucidate the exact anatomical substrate of dominant thalamic Korsakoff syndrome.

Combined third and sixth nerve paresis following optic nerve sheath fenestration

The authors report a case of transient third and sixth nerve paresis as a complication of optic nerve sheath fenestration in a patient with pseudotumor cerebri. The motility and pupillary abnormalities that are commonly associated with this procedure are reviewed briefly.

Vascular dementia: neuropathologic alterations and metabolic brain changes

After reviewing the concepts of dementia, in general, and vascular dementia, in particular, this review discusses potential future approaches that may contribute to an improved definition of the clinical syndrome and the neuropathological features of vascular dementia. Specific brain alterations in high-energy phosphate compounds, as measured by nuclear magnetic resonance, may contribute to the separation between dementias with neurodegenerative diseases and those with ischemic (vascular or hemodynamic) disorders.

Right motor neglect associated with dynamic aphasia, loss of drive and amnesia: case report and cerebral blood flow study

A 30-year-old right-handed man had right motor neglect, amnesia, aphasia and loss of drive following bilateral thalamic and subthalamic infarctions. Serial resting cerebral blood flow (CBF) measurements with either Xenon 133 inhalation or positron emission tomography at 1, 8 and 10 months post-onset showed a widespread and long-lasting low CBF in the cortex. An additional CBF measurement, during motor tasks, showed a marked interhemispheric asymmetry in the pattern of activation: whereas left hand movement resulted in a CBF increase in contralateral superior rolandic and prerolandic areas, no significant regional CBF changes were seen during right hand movement, despite recovery from motor neglect. This loss of CBF increase in cortical motor and premotor areas during voluntary movement of the previously neglected side points to a disruption of cortico-subcortical pathways subserving motor activation. The pathophysiology of aphasia, loss of drive and amnesia as well as their relationships to motor neglect, may also be discussed on the basis of thalamo-cortical disconnections.

The anterior choroidal artery does not supply the corona radiata and lateral ventricular wall

BACKGROUND AND PURPOSE

We sought first to characterize the clinical syndromes of patients found to have angiographic, computed tomographic, or magnetic resonance imaging scan indexes of anterior choroidal artery territory infarction and then to determine the frequency of involvement of the periventricular corona radiata in such patients.

METHODS

Sixteen patients were selected based on angiographically, or surgically, documented occlusion of the anterior choroidal artery or based on infarcts whose minimal lesions included the anterior choroidal territory as defined by Kolisko and Beevor. We mapped the lesions using the templates of the Matsui and Hirano atlas and entered them into a computer using a program allowing overlapping diagrams of the cases.

RESULTS

The anatomic distributions were fairly uniform, all involving the lower portion of the posterior limb of the internal capsule, the medial pallidum (75% of cases), cerebral peduncle in 44%, thalamus in 37%, and the medial temporal lobe in 38%. None extended outside these areas to include the upper corona radiata. The clinical picture corresponded to the well-established neurological syndrome featuring motor deficits with varying degrees of visual field and sensory impairments. Only two showed hypesthetic ataxic hemiparesis.

CONCLUSIONS

Our findings indicate that the syndrome of anterior choroidal artery infarction is fairly uniform; ataxic hemiparesis occurs infrequently; and lesions in the lateral ventricular wall and the corona radiata are not part of the territory supplied by the anterior choroidal artery.

Peduncular hallucinations

Peduncular hallucinations usually present as visual disorders and are often genuine hallucinations associated with thalamic and/or mesencephalic lesions. In this case report we describe the clinical findings in a patient with hallucinations. Magnetic resonance imaging demonstrated bilateral ischaemic lesions in the thalamus and in the mesencephalon. The pathogenesis of hallucinations in these disorders is discussed in the light of the findings provided by imaging techniques.

Isolated angiitis of the central nervous system: involvement of penetrating vessels at the base of the brain

Isolated angiitis of the central nervous system (IAC) was diagnosed in a 40-year-old Caucasian male by histological examination of a leptomeningeal biopsy specimen, and the exclusion of systemic inflammatory or infective disease. Therapy with prednisone 30 mg/day and cyclophosphamide 100 mg/day resulted in clinical and radiological improvement, which have been maintained for an 8-month follow-up period. Magnetic resonance imaging (MRI) showed lesions implicating involvement of specific penetrating vessels at the base of the brain, an unusual complication of IAC, and allowed an accurate MRI-clinical correlation.

Loss of psychic self-activation with bithalamic infarction. Neurobehavioural, CT, MRI and SPECT correlates

Two patients with bilateral thalamo-mesencephalic infarct in the paramedian territory developed vertical gaze dysfunction and marked behavioural changes, in the absence of significant motor inability and formal neuropsychological impairment. While they were physically and emotionally active before stroke, they became apathetic, aspontaneous, indifferent, and seemed to have lost motor and affectic drive, as well as the need itself for any psychic activity. However, this mental and motor inertia was reversible when the patients were repeatedly stimulated by another person. This need for constant external programming, together with a lack of emotional reactivity, made the patients resemble robots. CT and MRI suggested involvement of the dorsomedial and midline nuclei of the thalamus, and SPECT showed remote frontomesial hypoperfusion. A disturbance of the striatal-ventral pallidal-thalamic-frontomesial limbic loop is suggested by previous reports of a similar "loss of psychic self-activation", "pure psychic akinesia", or "athymhormia" with bipallidal, bistriatal, or subcortical bifrontal lesions.

Association of "top of the basilar" syndrome with megadolichobasilar artery. Clinical and neuroimaging evaluation

We describe the case of a patient with a history of trigeminal neuralgia who suddenly developed the "top of the basilar" syndrome. MRI disclosed ischemic lesions in the left paramedian mesencephalic tectum, in the left ventral thalamus, in the left occipital lobe and a megadolichobasilar artery (MDBA). The association of MDBA with the top of the basilar syndrome is rarely reported. We discuss the possible hemodynamic mechanism producing a top of the basilar syndrome in the presence of MDBA.

Aphonia due to paramedian thalamo-subthalamic infarction. Remarks on two cases

We describe two patients in whom CT brain scans imaged paramedian thalamo-subthalamic infarcts in the territory of the thalamo-mesencephalic arteries. Such infarcts give rise to a complex syndrome marked by disturbances of consciousness and of eye movement and neuropsychological disorders, including attentional, memory and, more rarely, language deficits. A loss of voice volume may accompany aphasic disturbances but is exceedingly rare in isolation. In the cases described the aphonia, total but transient, was the only language disorder. The physiopathological mechanisms involved in aphonia are complex and controversial.

Weber's syndrome with recovery: CT demonstration of an end-zone infarction in the territory of the mesencephalic artery

Weber's syndrome is one of the classically described brainstem syndromes. The mesencephalic artery and the syndromes resulting from occlusion of its branches have been attracting increasing interest in the past few years. We present here a case of Weber's syndrome emphasizing that (1) it is one of the major syndromes deriving from infarction in the territory of the mesencephalic artery; (2) that at least two clinical patterns of Weber's syndrome may be distinguished on the basis of the presence or lack of abnormal somnolence, mental confusion, and abulia; and (3) that each one of these patterns seems to be correlated with damage to distinct zones within the general territory of the mesencephalic artery.

Rediscovering tactile agnosia

Eighty-four patients with damage to various levels of the nervous system, ranging from the peripheral nerves to the cerebral cortex, underwent somesthetic assessment in order to determine the degree to which basic and complex perceptual and motor disorders affect tactile object recognition (TOR) and to determine whether TOR can be impaired in the absence of more basic sensorimotor imperception. The results suggest that (1) basic and intermediate disorders of somesthetic function impair TOR but are commensurately more severe for any given degree of TOR impairment in patients with peripheral lesions than in patients with cortical lesions; (2) neither hemiparesis nor hemianopia alone precludes normal TOR; (3) hemineglect contributes substantially to TOR impairment; (4) impairment of TOR can occur in the absence of more basic somesthetic dysfunction and constitutes tactile agnosia; (5) tactile agnosia is a subtle, nondisabling disorder that should be distinguished from the nonagnosic, severe and disabling disorder, astereognosis; and (6) tactile agnosia results from unilateral damage to parietotemporal cortices, possibly including the second somatosensory cortex, in either hemisphere.

Language disturbances from mesencephalo-thalamic infarcts. Identification of thalamic nuclei by CT-reconstructions

The authors report the cases of two patients with CT-documented paramedian mesencephalo-thalamic infarcts, showing language disturbances. The first patient showed a non fluent, transcortical motor-like aphasia, the other had a fluent but severely paraphasic language disorder. The CT study disclosed that it was the dorso-median thalamic nucleus that was mostly involved in both cases. These findings agree with a few previous pathological studies suggesting that the paramedian thalamic nuclei, particularly the dorso-median nucleus may play some role in language disturbances. However the anatomical basis for thalamic aphasia remains speculative, taking into account the importance of cortical connections in the origin of subcortical neuropsychological disturbances.

Meso-diencephalic infarction: a not so rare form of stroke

26 patients admitted with clinical pictures consistent with meso-diencephalic infarction were studied using computerized axial tomography, magnetic resonance imaging and angiography. All of the patients presented symptoms in two of three major categories which comprise the "top of the basilar" syndrome. Lesions in the territory of the basilar-communicating artery were demonstrated in 22 of them. The remaining patients died before adequate neuroimaging documentation was obtained. Overall prognosis appeared relatively good since 80% of the patients recovered completely or incompletely from the ictus. Meso-diencephalic infarction is a very important and not uncommon subtype of cerebrovascular disorder.

Distribution of neurofibrillary tangle formation and [3H]-D-aspartate receptor binding in the thalamus in the normal elderly brain, in Alzheimer's disease and in Parkinson's disease

The overactivity of glutamatergic neurons may underlie some neurodegenerative disorders, including Alzheimer's disease (AD). We explored the relationship between glutamatergic transmission and neurofibrillary tangle formation by measuring [3H]-D-aspartate binding activity and the proportion of neurons containing tangles within individual thalamic nuclei in five AD cases. Five elderly normal and five Parkinson's disease (PD) cases were used as controls. A highly significant correlation between [3H]-D-aspartate binding and tangle counts in Alzheimer's disease suggests that those thalamic nuclei which normally receive a relatively dense glutamatergic afferent input are predisposed to tangle formation. There were no significant differences in individual thalamic nuclear [3H]-D-aspartate binding between controls and the AD and PD groups.

Impairment of vertical motion detection and downgaze palsy due to rostral midbrain infarction

We present two cases with acute onset of vertical gaze palsy, mainly consisting of impaired downgaze and apraxia of downward head movements, together with neuropsychological deficits (hypersomnia, impaired attention and disorders of memory and affective control). CT and MRI revealed bilateral post-ischaemic lesions in the dorsomedial thalamus and the mesodiencephalic junction, dorsomedial to the red nucleus, thus being restricted to the territory of the posterior thalamosubthalamic paramedian artery, which includes the region of the rostral interstitial nucleus of the medial longitudinal fascicle as the main premotor nucleus for the generation of vertical saccades. In our patients, oculographic examination with electro-oculography and magnetic search coil recording showed severe impairment of downward more than upward saccades and only minor deficits of vertical pursuit and the vestibulo-ocular reflex. Visual functions were normal, with one exception: a psychophysical test of motion perception revealed a significant deficit in the detection of vertical movements. This could be due to a central adaptive mechanism which, in order to minimize oscillopsia, might elevate thresholds for vertical motion perception in cases of vertical gaze palsy. As an alternative explanation, lesions within the midbrain tegmentum could have damaged subcortical visual pathways involved in motion perception.

Paramedian thalamic and midbrain infarcts associated with palilalia

A patient with paramedian thalamic and midbrain infarcts developed palilalia.

Mesolimbocortical dementia: clinico-pathological studies on two cases

The clinicopathological findings are presented of two cases of mesolimbocortical dementia. Both cases were characterised by late onset slowly progressive personality changes and progressive intellectual deterioration without clinical Parkinsonism. Neuropathological findings revealed non-specific neuronal degeneration, Holzer and GFAP positive gliosis primarily affecting the limbic system, caudate, thalamus and substantia nigra. The pathological findings coincide with the distribution of the non-striatal dopaminergic pathways and suggest an intrinsic involvement of these pathways to account for the clinical and pathological manifestations.

Reversible bilateral thalamic lesions caused by primary internal cerebral vein thrombosis: a case report

The case is reported of a patient with primary thrombosis of the internal cerebral veins who presented initially with unilateral and later developed bilateral thalamic lesions revealed by computed tomography. Magnetic resonance imaging and angiography confirmed the diagnosis. Upon anticoagulation the patient recovered nearly completely.

Syndrome of downward gaze paralysis, amnesia and hypersomnolence

A 60 year old woman with computed tomographic-verified bilateral thalamic infarction is described. She demonstrated downward gaze paralysis, amnesia and hypersomnolence. On the functional level such tasks as walking and eating were disconcerting. Although there have been only a few reports of the complete triad it may be more common than realized and represents a distinct syndrome that can be identified by the bedside.

Description of brain injury in the amnesic patient N.A. based on magnetic resonance imaging

N.A. has been amnesic since 1960 when at the age of 22 years he sustained a penetrating brain injury with a miniature fencing foil. The amnesia primarily affects verbal material and occurs in the absence of other detectable cognitive deficits. Previous CT scans demonstrated a lucency in the region of the left mediodorsal thalamic nucleus, but no additional damage was revealed. Beginning in 1986 when he was 48 years old, N.A. was evaluated with a series of magnetic resonance imaging (MR) studies. Three major areas of damage were identified. In the left thalamus there is a prominent 3- to 4-mm-wide linear lesion that approximates the position and orientation of the internal medullary lamina. The defect extends for approximately 20 mm anteroposteriorly and likely involves the rostral group of intralaminar nuclei (central medial, paracentral, central lateral, rhomboid, and reuniens nuclei), the caudal group of intralaminar nuclei (centrum medianum and parafascicular nuclei), the ventral aspect of the mediodorsal nucleus, and the ventral lateral and ventral anterior nuclei. It also likely interrupts the trajectories of the mammillothalamic tract and postcommissural fornix. The posterior hypothalamus is markedly disrupted and the mammillary nuclei appear to be missing bilaterally. Finally, the right anterior temporal lobe is damaged for a distance of about 3.5 cm from the pole to midway through the amygdaloid complex. This damage probably occurred during exploratory neurosurgery done at the time of N.A.'s injury. The hippocampal formation appears intact on both sides. A comparison of these findings with those from other patients with diencephalic amnesia suggests that amnesia can result when several diencephalic structures are damaged conjointly, including the internal medullary lamina, the intralaminar nuclei, the mediodorsal nucleus, and the mammillothalamic tract. Whether amnesia as severe as N.A.'s would result from selective damage to any one of these structures remains to be determined.

Aphemia associated with bilateral striato-capsular lesions subsequent to cerebral anoxia

A case is presented of a 13-year-old right-handed male who exhibited bilateral striato-capsular lesions following an episode of cerebral anoxia and a range of clinical features typical of aphemia. The findings of a neurological assessment, neuroradiological assessment and battery of speech/language tests are described and their implications for current theories regarding the role of the basal ganglia in speech/language function discussed. The patient initially demonstrated an isolated loss of the ability to articulate words without the loss of the ability to write or comprehend spoken language. His initial mutism later resolved into a dysarthria with features similar to those seen in hypokinetic dysarthria. It was concluded that striato-capsular lesions in childhood are capable of producing temporary language disturbances and in some cases a persistent dysarthria.

Mnemonic and neuropathological effects of occluding the posterior cerebral artery in Macaca mulatta

To investigate experimentally the mnemonic and neuropathological effects of blockage of the posterior cerebral arteries (PCA), a cerebrovascular accident that can lead to global anterograde amnesia in humans, we permanently occluded these arteries bilaterally in six monkeys and then evaluated their performance on a visual recognition task, after which we assessed the extent of their ischemic infarcts. The latter showed substantial individual variation, ranging from almost no damage in one case to massive unilateral injury of both the ventromedial o occipitotemporal cortex and hippocampal formation in another. In the four remaining cases, however, the infarcts fell within a narrow range, being confined almost entirely to the hippocampal formation and parahippocampal gyrus, and then only to restricted portions of these structures, unilaterally in one case, and bilaterally in the three others. Performance on the recognition task was related to the presence and bilaterality of the hippocampal injury. Thus, the case without any hippocampal damage performed at a rate equal to that of normal controls; the case with unilateral hippocampal damage was mildly impaired; and the three cases with bilateral infarctions, involving between 20 and 55% of the hippocampal formation, showed substantial impairment, with scores averaging 20% below those of normal controls. The only subfields of the hippocampus damaged in common in these cases were CA1 and CA2. Paradoxically, the memory loss found in these three animals with only partial bilateral hippocampal damage was significantly greater than that found in animals with total bilateral ablation of the hippocampal formation, whose scores averaged only 10% below those of normal controls. Possible explanations for this extremely puzzling outcome are proposed.

Diencephalic amnesia: a reorientation towards tracts?

The principal thalamic and hypothalamic structures implicated in mnemonic information processing are the mediodorsal nucleus of the thalamus, the pulvinar, anterior thalamus, and laterodorsal nucleus, the mamillary body, and the mamillothalamic tract and internal medullary lamina. Determining the contribution of an individual region in memory is quite difficult as it is nearly impossible to find a circumscribed damage of only one region. On the contrary, some illnesses affecting primarily the diencephalon, such as Korsakoff's disease, tend to involve several structures together. Furthermore, even when cases with similar circumscribed diencephalic damage can be found, these will not necessarily demonstrate the same outcome on the behavioral level. Therefore, the role or contribution of individual memory-related diencephalic structures has to be inferred by comparing a number of cases and by then extracting distinct features common to a given group. Such an approach revealed that the contributions of the two fiber systems mentioned above, mamillothalamic tract and internal medullary lamina, might be more important in processing information long-term than had been acknowledged previously and might be more important than that of the nuclear masses mentioned, especially of the mediodorsal thalamus. This outcome underlines the view that emphasizing interactions between brain regions rather than single static masses will provide a more realistic picture of how the nervous system acts in information processing.

The neuropsychology of paramedian thalamic infarction

A longitudinal study of three patients with CT-scan documented paramedian thalamic infarctions (bilateral, primarily right, unilateral left) is reported and the neuropsychology of human paramedian thalamic infarction is reviewed. The neuropsychological deficits following these selected lesions, the nature of the clinical memory disorder, and the neuroanatomy of memory are discussed. The significance of cortical/subcortical relationship in explaining observed behavioral changes is emphasized. Brain damage with maximum involvement in the dorsomedial nuclei and mamillothalamic tracts appears to cause primarily a memory disorder and frontal-limbic behavioral changes, the severity and profile of deficits depending on lesion extent and location. Both anterograde and remote memory loss may be present. Asymmetry in memory at the level of the thalamus was observed, following the left-verbal, right-nonverbal dichotomy.

Generalized epileptic seizures as the presenting symptom of lacunar infarction in the brain

Five elderly hypertensive patients presented with grand mal seizures and had computed tomographic (CT) findings consistent with lacunar infarction. Three of them had also a recent hemiparesis, contralateral to the side of the CT findings. Follow-up CT scans supported the diagnosis of lacunar infarction. Contrary to the accepted opinion, generalized epileptic seizures may be the presenting symptom of lacunar brain infarction.

Dementia due to vascular disease--a multifactorial disorder

This review was undertaken to evaluate critically the literature pertaining to vascular dementia with the objective of determining a more useful and scientifically supported definition of vascular dementia, its relation to other causes of dementia, and the biologic mechanisms involved in its causation.

"Top of the basilar" syndrome: a comparison of clinical and MR findings

Among 100 patients with an infarction of the brain reported on MR and clinically confirmed there were 4 with widespread lesions of the temporal and occipital lobes, thalamus, midbrain, pons and cerebellum, all supplied by arteries originating around the top of the basilar artery. Clinically these patients presented the "top of the basilar" syndrome, which is caused by a disturbance in circulation at the top of the basilar artery. Which brain areas are involved may be deduced theoretically from the vascular anatomy. These lesions can, we believe, be clearly detected using MR, because of its sensitivity to ischaemic disturbances and in the posterior fossa. We report our 4 patients here to illustrate the clinical presentation and MR findings of the "top of the basilar" syndrome.

Amnesia following thalamic hemorrhage. Another stroke syndrome

The clinical manifestations of thalamic hemorrhage frequently comprise hemiparesis, hemianesthesia, and oculomotor abnormalities. Since the advent of computed tomography, an amnestic syndrome following thalamic hemorrhage has been recognized, but the thalamic structures involved and the mechanism of amnesia have remained uncertain. We report a patient with sudden memory dysfunction following hemorrhage into the anterior nucleus of the left thalamus that was shown neuropathologically to disrupt the mamillothalamic fasciculus, one of the principal components of the limbic system. It is considered that the amnestic syndrome following thalamic (anterior nucleus) hemorrhage is due to interruption of the mamillothalamic fasciculus.

Preserved learning of novel information in amnesia: evidence for multiple memory systems

Four of five patients with marked global amnesia, and others with new learning impairments, showed normal processing facilitation for novel stimuli (nonwords) and/or for familiar stimuli (words) on a word/nonword (lexical) decision task. The data are interpreted as a reflection of the learning capabilities of in-line neural processing stages with multiple, distinct, informational codes. These in-line learning processes are separate from the recognition/recall memory impaired by amygdalohippocampal/dosomedial thalamic damage, but probably supplement such memory in some tasks in normal individuals. Preserved learning of novel information seems incompatible with explanations of spared learning in amnesia that are based on the episodic/semantic or memory/habit distinctions, but is consistent with the procedural/declarative hypothesis.

Trans-mesencephalic arteries and veins. Angiographic aspects in tectal vascular lesions

The authors present the trans-mesencephalic arteries and their rôle in the differentiation of pure and secondary vein of Galen arterio-venous malformations (AVM). They illustrate the trans-mesencephalic draining veins of the so-called venous angiomas, which are normal variants, often associated with cavernous haemangiomas representing the clinically active lesion.

Bilateral traumatic third nerve palsy

Bilateral palsy of the third cranial nerve in a head-injured patient is described. Delayed computed tomography scanning demonstrated a midline necrotic lesion within the mesencephalon ventral to the aqueduct. The lesion, possibly the sequela of a focal contusion, involved both third nerve nuclear complexes and caused paralysis of their voluntary as well as autonomic functions. Gaze mechanisms and long tracts appeared to be less heavily damaged. The literature dealing with third nerve palsy, particularly bilateral cases, from traumatic and other origins is briefly reviewed.

Aphonia as the only speech disturbance from bilateral paramedian thalamic infarction

We examined a 55-year-old right-handed woman showing transient coma, amnesia, mild right hemiparesis, vertical gaze impairment and aphonia without aphasia. CT-scanning revealed bilateral paramedian thalamic infarction in the territory of the thalamo-subthalamic paramedian arteries. Aphonia may occur as a consequence of thalamic lesions, but until now it has not been described as an isolated speech disturbance.

Manic delirium and frontal-like syndrome with paramedian infarction of the right thalamus

A disinhibition syndrome affecting speech (with logorrhoea, delirium, jokes, laughs, inappropriate comments, extraordinary confabulations), was the main manifestation of a right-sided thalamic infarct involving the dorsomedian nucleus, intralaminar nuclei and medial part of the ventral lateral nucleus. Resolution of conflicting tasks was severely impaired, suggesting frontal lobe dysfunction. These abnormalities correlated with the finding on SPECT of a marked hypoperfusion in the overlying hemisphere predominating in the frontal region. We suggest that this behavioural syndrome was produced by disconnecting the dorsomedian nucleus from the frontal lobe and limbic system.

A case of cerebello-pontine angle infarction found by vertebral angiography

A patient was admitted complaining of sudden vertigo. Otoneurological examinations, electronystagmography (ENG), and vertebral angiography (VAG) showed constriction of vertebral artery and anterior inferior cerebellar artery, and basilar artery obstruction. Based on these findings, we diagnosed the case as posterior cranial fossa infarction. Computed tomography (CT) and magnetic resonance imaging (MRI) findings were negative. The authors conclude that VAG should be performed in certain cases of vertigo thought to be of central nervous origin when CT and MRI findings are both negative.

"Top of the basilar" syndrome: clinico-radiological evaluation

Sixteen patients having infarction caused by circulatory disturbance at the top of the basilar artery, that is to say, the "top of the basilar" syndrome, were studied, the diagnosis having been made by computerized tomography. Infarcts were widely distributed in each patient between the thalamus, midbrain, pons, cerebellum, and occipital lobe. Both thalami were involved in 7 cases. When the thalamus was involved bilaterally, the low density areas were symmetrical in size and localization. Angiography revealed that stenosis or occlusion lay within a circle 2 cm in diameter surrounding the five-forked junction at the top of the basilar artery in 84.6%. Recanalization of the occluded artery occurred in 61.5%, suggesting that embolism played an important role in appearance of this syndrome.

Bilateral paramedian thalamic artery infarcts: report of eight cases

Eight consecutive patients with CT scan evidence of a bilateral infarct in the territory of the paramedian thalamic artery are reported. In seven cases the infarct also extended to the territory of the polar artery. The main symptoms were: disorder of vigilance which cleared in a few days, and hypersomnolence which lasted longer and in two patients was still present a year later; amnesia, detectable clinically in four patients and only with tests in two patients, which persisted in one patient for three years; changes of mood and bulimia present in five and four patients respectively; and vertical gaze paresis in five patients. Only one patient died, and in the remainder the symptoms tended to subside, but none of the patients who could be followed-up for a year returned to normal behaviour. Clinical and CT scan correlations pointed to the mammillo-thalamic tract as the structure whose damage was responsible for the memory disorders.