A case of partial fascicular oculomotor paresis caused by midbrain infarction]

We report a 74-year-old man with an ischemic lesion in the ventral midbrain. He presented with contralateral ptosis and marked upward gaze paresis of the right eye. Neurological examination revealed partial oculomotor nerve palsy caused by impairment of the right levator palpebrae, superior rectus and inferior oblique muscles. This finding is highly suggestive of a possible lesion in the midbrain affecting the oculomotor fascicular fibers. Magnetic resonance images showed an ischemic lesion in the paramedian area of the right midbrain tegmentum. The coronal view of T 2-weighted imaging clearly demonstrated to be the site of lesions below the red nucleus. It seemed to be coincidental with the impaired site of involving the caudal part of oculomotor fascicular fibers emerging from the nucleus. This report is considered to be a typical case of partial fascicular oculomotor paresis based on impairment of the caudal part of oculomotor fascicles for the levator palpebrae, superior rectus, and inferior oblique muscles. This is a valuable case to be documented in which neurological site of lesions are consistent with those found in radiological study.     

Constant error of visual egocentric orientation in patients with acute vestibular disorder.

Errors of visual egocentric localization are well-known in patients with paresis of ocular muscles or paresis of conjugate gaze. In the present paper a series of patients with unilateral vestibular disorder disclosed a constant lateralization of the visual agocentre in the absence of any ocular paresis. The perceptual illusion is associated with an altered resting position of the eyes caused by the vestibular imbalance. The disturbance of visual, egocentric localization was revealed only after elimination of the visual frame of reference and the extent of lateralization of the visual egocentre was proportional to the degree of resting deviation of the eyes. Although the findings are of limited clinical importance they have a considerable theoretical interest. From the clinical point of view they may provide a basis for further understnading of the complex-perceptual illusions which may accompany disorders affecting central vestibulo-ocular connections. The results indicate that the perceptual effects are related to an altered central evaluation of the oculomotor programme and thus depend upon the operation of an 'efference copy'. This hypothesis is discussed with reference to earlier and current theories of visual localization.     

Dissociation of egocentric and allocentric coding of space in visual search after right middle cerebral artery stroke

Spatial representations rely on different frames of reference. Patients with unilateral neglect may behave as suffering from either egocentric or allocentric deficiency. The neural substrates representing these reference frames are still under discussion. Here we used a visual search paradigm to distinguish between egocentric and allocentric deficits in patients with right hemisphere cortical lesions. An attention demanding search task served to divide patients according to egocentric versus allocentric deficits. The results indicate that egocentric impairment was associated with damage in premotor cortex involving the frontal eye fields. Allocentric impairment on the other hand was linked to lesions in more ventral regions near the parahippocampal gyrus (PHG).     

Paroxysmal Hemipareses in Childhood

The authors report three patients suffering since infancy from transient attacks of paresis. The flaccid pareses most frequently affect the extremities in a hemiplegic fashion, but occasionally there is monoparesis or quadriparesis. The laterality and degree of the paresis are variable. Conciousness is always preserved, and in two cases attacks were preceded by ocular motor disturbances (skew deviation, nystagmoid jerks and conjugate deviations). Exceptionally, the transient hemiparesis may be preceded by a grand mal epileptic fit, though they are more likely to appear sporadically and independently of the paretic changes. In the interparoxysmal periods the children showed pronounced hypotonia, hyperkinetic extrapyramidal features and oligophrenia. Neuroradiological procedures have excluded brain anomalies of vascular or other aetiology and simple biochemical analyses were negative. EMG during paretic periods have revealed central motor neuron lesions, while EEG demonstrated non-specific paroxysmal features. A brain-stem dysfunction in the aetiology is postulated.     

Isolated acquired unilateral horizontal gaze paresis from a putative lesion of the abducens nucleus.

In three patients, acute horizontal gaze pareses developed that could not be overcome with the oculocephalic maneuver, indicating a putative lesion of the ipsilateral abducens nerve nucleus. None of the patients had a facial nerve paresis or evidence of a trigeminal sensory neuropathy. Although most lesions that affect the abducens nerve nucleus also damage the ipsilateral fasciculus of the facial nerve, small lesions in this region can produce an isolated horizontal gaze paresis.     

Horizontal gaze paresis in hemispheric stroke

Of 156 stroke patients prospectively and consecutively evaluated, one-third had a homonymous hemianopia. Of those 52 patients, 46% had a horizontal conjugate gaze paresis at the time of presentation. This gaze paresis was most commonly seen with large hemispheric stroke. The overall prognosis in patients with a gaze paresis was poor. The 30-day case fatality rate was 49% which was significantly higher than for stroke patients presenting with homonymous hemianopia without a gaze paresis.     

Unusual MR findings of Wernicke encephalopathy with cortical involvement]

We report a 48-year-old chronic alcoholic man, who developed consciousness disturbance, oculomotor paresis, and flaccid tetraplegia. His dietary habit was very poor since one month prior to the present admission and he was drinking alcoholic beverage. On admission on April 19, 1999, he showed disturbance of consciousness, tetraparesis without sensory disturbance, gaze paresis, and vertical nystagmus on downward gaze. His blood thiamine level was 12 ng/ml (normal range: 23.8-45.9). MRI demonstrated symmetric hyperintense lesions in the motor and premotor cortices bilaterally, in addition to other changes indicating Wernicke's encephalopathy. His motor weakness and oculomotor disturbance improved after treatment with intravenous thiamine. His cortical MRI also normalized. We believe that his cortical abnormality was responsible for his motor paresis and this is an unusual and unique finding for Wernicke's encephalopathy.     

Gaze direction determination in schizophrenia

It has been proposed that an impairment in gaze determination is responsible for the paranoid symptoms reported in schizophrenia. To address this, we examined the gaze discrimination system in schizophrenia. Thirty-two patients suffering from schizophrenia (20 patients with persecutory delusions and 12 patients without such delusions) were compared to 32 control subjects on two specific tasks. In the first task, the subjects had to determine whether 130 portraits were looking right or left. In the second task the subjects were asked to determine whether or not 130 portraits were looking at them.The absolute threshold of difference used to investigate the influence of instruction on gaze discrimination did not show any difference between patients with schizophrenia, whatever paranoid or not, and control subjects. Paranoid patients, as well as controls, displayed a significantly finer discrimination threshold in the right vs. left judgment than in the self vs. non-self judgment. Subjects with schizophrenia were able to discriminate gaze direction in the two tasks, but they took significantly more time in the task requiring to determine the presence or the absence of a mutual gaze contact than in the other one, whereas controls took the same duration to elicit both tasks. These data are consistent with those reporting that perceptual abilities are spared in schizophrenia while delusions are related to an impairment of a higher level of analysis.     

A case presenting vertical one-and-a-half syndrome and seesaw nystagmus due to thalamomesencephalic infarction]

A 58-year-old woman presented, conjugate upgaze palsy and monocular paresis of downward gaze in the ipsilateral eye (vertical one-and-a-half syndrome; VOHS) as well as seesaw nystagmus (SSN). Vertical oculocephalic response and conjugate horizontal gaze were preserved. Magnetic resonance imaging revealed a right thalamo-mesencephalic infarction including the rostral interstitial nucleus of the medial longitudinal fasciculus (riMLF) and the interstitial nucleus of Cajal. On the 22nd hospital day SSN was disappeared, and then on the 32nd day VOHS was improved. The lesions of VOHS may have affected the efferent tracts of riMLF and the descending fibres to the ipsilateral subnucleus of the inferior rectus and contralateral subnucleus of the superior oblique. Furthermore, it was assumed that SSN was caused simultaneously by a lesion in the interstitial nucleus of Cajal existing in the adjacent area of riMLF.     

Supranuclear gaze palsy following extracorporeal surgery with induced hypothermia. Report of two cases

Although up to 5-20% of the patients who underwent surgery with hypothermia and cardiac arrest may present neurological complications, just a few cases of ocularmotor disorders have been described. Acquired supranuclear ocular motor paresis (ASOMP) is a rare disorder characterized by impairment in volitional and reflex saccades and smooth pursuit in one or more directions of gaze with intact extraocular movements in response to vestibular estimulation. We present two cases of acquired supranuclear ocular motor paresis associated with a peculiar gait disorder. Although a partial improvement was observed, both patients continue with ocular motor paresis in vertical direction after one year of evolution. A selective vulnerability of certain brainstem neuronal groups would explain the pathophysiology of these symptoms.     

Clinical spectrum of Niemann-Pick disease type C

Analysis of the neurologic symptomatology in 22 patients with Niemann-Pick disease type C revealed 3 phenotypes: (1) an early-onset, rapidly progressive form associated with severe hepatic dysfunction and psychomotor delay during infancy and later with supranuclear vertical gaze paresis, ataxia, marked spasticity, and dementia; (2) a delayed-onset, slowly progressive form heralded by the appearance, usually in early childhood, of mild intellectual impairment, supranuclear vertical gaze paresis, and ataxia, and later associated with dementia and, variably, seizures and extrapyramidal deficits; (3) a late-onset slowly progressive form distinguished from the 2nd pattern by later age of onset (adolescence or adulthood) and a much slower rate of progression. The existence of the 1st and 2nd phenotypes within the same sibship suggests that they are variant expressions of the same clinicopathologic disorder. Niemann-Pick disease type C should be considered not only in infants and children who present with organomegaly and a progressive neurodegenerative course, but also in adolescents and adults who have insidiously progressive neurologic dysfunction and only slight organomegaly. Associated with the disease is a marked deficiency in the ability of cultured fibroblasts to esterify exogenously supplied cholesterol. Assay of this deficiency is particularly useful for confirming the diagnosis in patients with atypical presentation.     

The clinical and computed tomographic features of cerebellar peduncular hemorrhage

Three patients with medial ventral cerebellar peduncular hemorrhages presented with a characteristic syndrome. This included (1) ipsilateral ataxia, (2) lower motor neuron type facial weakness, and (3) ipsilateral gaze paresis. The gaze paresis could not be overcome with a doll's head maneuver. The findings are explained by compression of the facial colliculus, with involvement of the sixth nerve nucleus and the middle cerebellar peduncle. Two patients were hypertensive; one was normotensive, and no etiology was identified with angiography. Of 40 patients with cerebellar hemorrhage seen at our institution, only those with medial cerebellar peduncular hematomas demonstrated this clinical triad, and we have not seen this clinical triad in other pathologic conditions. The diagnosis of a small medial cerebellar peduncular hemorrhage was established by CT. In two patients, repeat CT showed complete hematoma resolution. The patients shared a favorable prognosis.     

Tuberous sclerosis: relationships between topographic mapping of EEG, VEPs and MRI findings

A group of 10 patients suffering from tuberous sclerosis (TS) and epilepsy was studied by means of topographic mapping of EEG and visual evoked potentials. The localizing ability of the technique was compared to the topography of hyperintense T2-dependent areas seen on magnetic resonance images (MRI). Data were collected from 19 electrodes, free from interictal EEG transients and artifacts, spectral analysis was performed using the FFT algorithm and color maps were produced by specialized equipment. Data were analyzed with respect to the presence of interhemispheric asymmetries and significant differences with age-matched normal controls. The topography of slow frequency components was the best clue for localization, with a concordance between imaging and spectral EEG data in 76% of the lesions detected by MRI. In 7 patients topographic mapping revealed spectral abnormalities in areas where MRI was not able to detect morphological lesions. These abnormalities were characterized by an increased delta (5 patients), theta (4 patients), or lowered ipsilateral alpha (1 patient) power. Although full agreement between imaging and electrophysiological data was not observed, we believe that in patients with TS the study of EEG rhythm activity can add valuable information to the visual inspection of the tracings.     

Ocular and head movements in infarctions of the thalamic region

Oculomotor disorders in 22 infarctions in the thalamic region are recorded. Clinical examination and electro-oculography (17 cases) showed that paramedian thalamo-subthalamic lesions were responsible for clear deficits: upgaze paralysis and in some cases downgaze paralysis, partial paresis of the oculomotor nerve, deficits of lateral eye movements, myosis, paralysis of head flexion combined with downgaze paralysis. Postero-median choroid artery infarction was associated with upgaze paresis, slight deficit of lateral eye movements and myosis. Postero-lateral choroid artery infarction resulted in a partial visual field defect and in some cases, a contralateral hypometria; myosis was slight and inconstant. Infarctions of the internal capsule (anterior choroid artery, deep branches of the middle cerebral artery) were associated with a deficit of contralateral saccades. Ocular pursuit, when possible, was often saccadic, whatever the site of the infarction. This prevailed with gaze towards the lesion side.     

A case of primary progressive multiple sclerosis with onset of memory impairment]

We report a 52-year-old woman with primary progressive multiple sclerosis (PPMS) presenting with chronic progressive memory impairment. From a couple of years prior to admission, she had developed impairment of her short-term memory. For example, she forgot her nephew's name, and spoke the same phrases again and again. She also sometimes forgot to turn off her gas stove and forgot things she bought in shops. Moreover, her mental activity gradually decreased and she became apathetic. However, she did not note her memory impairment, and had no hallucinations. She was admitted to our hospital on 20 May, 2003 because donepezil had been ineffective for treating her memory impairment. Neurologically, she showed bilateral horizontal gaze nystagmus, mild limb ataxia on the left and mildly ataxic gait. Neuropsychological examinations showed mildly impaired cognitive function, e.g., MMSE 25/30, WAIS-R full IQ 69 and especially in verbal short memory, which may represent temporal lobe dysfunction. Moreover, Benton's visual memory test revealed marked visual short-term memory impairment, while impaired performance on a Kana picking up test suggested mild to moderate attention impairment, which could have represented frontal lobe dysfunction. Brain MRI showed multiple T2-high plaque lesions close to the bilateral lateral ventricles, and bilateral optic nerve lesions enhanced by gadolinium. Also, spinal cord MRI showed a gadolinium enhanced lesion at Th5 on the left. Cerebral spinal fluid (CSF) examination showed normal cell count and protein level, and undetectable oligoclonal bands (OCB), but an elevated IgG index (1.1, normal < 0.85). Visual evoked potentials (VEPs) showed prolonged P100 latency bilaterally, indicating subclinical optic nerve lesions. She was thus diagnosed as having PPMS according to McDonald's diagnostic criteria for MS. 99mTc Single photon emission computed tomography (SPECT) showed a decreased cerebral blood flow (CBF) in the bilateral frontal and temporal lobes, which was consistent with her clinical features. PPMS patients generally present with chronic progressive spastic paraparesis and/or cerebellar ataxia. Cognitive impairments observed in PPMS are generally thought to be due to white matter lesions, i.e., subcortical dementia. However, some recent reports have shown MS patients with short-term memory impairment (antegrade amnesia) similar to cortical dementias such as Alzheimer's disease (AD). In such MS cases, visual short-term memory impairment seems characteristic of their cognitive impairment compared to AD cases. As well, the present case showed visual memory impairment as evaluated by Benton's memory test. Parietal and frontal lobes are reported to be important for verbal and visual working memory, respectively. Thus, in the present case, decreased CBF in the frontal and temporal lobes, which could have been due to a disconnection between cortices and subcortices caused by the white matter lesions, is consistent with the type of her cognitive dysfunction, i.e., notable visual memory impairment. PPMS may thus be an important disease as a differential diagnosis for chronic progressive dementia. Further neuropsychological and functional imaging studies will be necessary to achieve a better understanding of the mechanisms of cognitive impairment in PPMS.     

Ocular motor ability and covert attention in patients with Duane Retraction Syndrome

Is orienting of spatial attention dependent on normal functioning of the ocular motor system? We investigated the role of motor pathways in covert orienting (attentional orienting without performing eye movements) by studying three patients suffering from Duane Retraction Syndrome—a congenital impairment in executing horizontal eye movements restricted to specific gaze directions. Patients showed a typical exogenous (reflexive) attention effect when the target was presented in visual fields to which they could perform an eye movement. This effect was not present when the target was presented in the visual field to which they could not perform eye movements. These findings stress the link between eye movements and attention. Specifically, they bring out the importance of the ability to execute appropriate eye movements for attentional orienting. We suggest that the relevant information about eye movement ability is provided by feedback from lower motor structures to higher attentional areas.     

Oscillopsia: pathophysiological mechanisms and treatment

Oscillopsia is an illusion of an unstable visual world. It is associated with poor visual acuity and is a disabling and stressful symptom reported by numerous patients with neurological disorders. The goal of this paper is to review the physiology of the systems subserving stable vision, the various pathophysiological mechanisms of oscillopsia and the different treatments available. Visual stability is conditioned by two factors. First, images of the seen world projected onto the retina have to be stable, a sine qua non condition for foveal discriminative function. Vestibulo-ocular and optokinetic reflexes act to stabilize the retinal images during head displacements; ocular fixation tends to limit the occurrence of micro ocular movements during gazing; a specific system also acts to maintain the eyes stable during eccentric gaze. Second, although we voluntary move our gaze (body, head and eye displacements), the visual world is normally perceived as stable, a phenomenon known as space constancy. Indeed, complex cognitive processes compensate for the two sensory consequences of gaze displacement, namely an oppositely-directed retinal drift and a change in the relationship between retinal and spatial (or subject-centered) coordinates of the visual scene. In patients, oscillopsia most often results from abnormal eye movements which cause excessive motion of images on the retina, such as nystagmus or saccadic intrusions or from an impaired vestibulo-ocular reflex. Understanding the exact mechanisms of impaired eye stability may lead to the different treatment options that have been documented in recent years. Oscillopsia could also result from an impairment of spatial constancy mechanisms that in normal condition compensate for gaze displacements, but clinical data in this case are scarce. However, we suggest that some visuo-perceptive deficits consecutive to temporo-parietal lesions resemble oscillopsia and could result from a deficit in elaborating spatial constancy.     

A case of divergence palsy associated with bilateral chronic subdural hematoma

A surgical case of bilateral chronic subdural hematoma presenting with divergence palsy is reported. A 75-year-old female was admitted to hospital for investigation of 2-week history of diplopia. The initial neurological examination demonstrated no abnormal findings except Hess chart suggesting bilateral concomitant strabismus or paresis of lateral rectus on both eyes. Because of the homonymous diplopia disappeared when the object of fixation in brought closer and the patient showed no impairment of gaze movements and following movements, the patient was diagnosed as divergence palsy and referred to the Neurosurgical Service. The physical examination revealed a 75-year-old, alert, fully oriented with diplopia at distant gaze. A computerized tomographic (CT) scan showed bilateral subdural hematoma. Emergency burrhole evacuation was performed and total amount bilateral hematoma was 220ml. Diplopia disappeared postoperatively. Hess chart examined two months after the operation shows no impairment of divergence function. This is the first reported case of divergence palsy associated with bilateral chronic subdural hematoma in CT era.     

Object identification in cerebral visual impairment characterized by gaze behavior and image saliency analysis

Individuals with cerebral visual impairment (CVI) have difficulties identifying common objects, especially when presented as cartoons or abstract images. In this study, participants were shown a series of images of ten common objects, each from five possible categories ranging from abstract black & white line drawings to color photographs. Fifty individuals with CVI and 50 neurotypical controls verbally identified each object and success rates and reaction times were collected. Visual gaze behavior was recorded using an eye tracker to quantify the extent of visual search area explored and number of fixations. A receiver operating characteristic (ROC) analysis was also carried out to compare the degree of alignment between the distribution of individual eye gaze patterns and image saliency features computed by the graph-based visual saliency (GBVS) model. Compared to controls, CVI participants showed significantly lower success rates and longer reaction times when identifying objects. In the CVI group, success rate improved moving from abstract black & white images to color photographs, suggesting that object form (as defined by outlines and contours) and color are important cues for correct identification. Eye tracking data revealed that the CVI group showed significantly greater visual search areas and number of fixations per image, and the distribution of eye gaze patterns in the CVI group was less aligned with the high saliency features of the image compared to controls. These results have important implications in helping to understand the complex profile of visual perceptual difficulties associated with CVI.     

Hemispheric contributions to drawing

The drawings of 69 consecutive stroke patients with single cerebral lesions on CT and of 33 normal controls, were analyzed by two independent observers using a standardized scoring system. The drawings of left brain damaged subjects (LBD) were more impaired overall than those of right brain damaged subjects (RBD). RBD drawings displayed hemispatial neglect and impaired spatial relationships. LBD drawings were simplified and exhibited low level errors of execution. Lesion size correlated significantly with drawing impairment in RBD but not in LBD. No relationship between intrahemispheric lesion location and drawing quality was found. However, severity of hemiparesis correlated significantly with drawing impairment in LBD. Performance on a visuospatial perceptual task correlated better with overall drawing quality for RBD than for LBD. Our data suggest that neglect and a visuospatial deficit impair drawing in RBD while dominant hand paresis and a conceptual impairment which parallels comprehension impairment contribute to LBD drawing disability.