Anterior Visual Pathway Dysfunction Research Articles

Neuromyelitis optica with brain stem involvement in a middle-aged Ethiopian woman: a case report and review of literature

IntroductionNeuromyelitis optica is a demyelinating disease of the central nervous system that predominantly affects the optic nerves and spinal cord. In neuromyelitis optica, white blood cells and antibodies primarily attack the optic nerves and the spinal cord, but may also attack the brain. Brainstem manifestation has been described recently. So far, neuromyelitis optica is very rare in Ethiopia and there were only two case reports, but this is the first case report of neuromyelitis optica with brainstem involvement.Case presentationA 47-year-old Addis Ababa woman presented to Saint Paul’s Hospital Millennium Medical College with a history of visual loss of 7 years and bilateral lower limb weakness of 4 days duration. She had bilateral oculomotor nerve palsy. Her past medical history showed systemic hypertension for 18 years and dyslipidemia for 1 year. The objective evaluation of the patient revealed right optic nerve atrophy suggesting optic neuritis and flaccid paraplegia with sensory level at the fourth thoracic vertebra. Diagnostic work-up using electromyography and spinal magnetic resonance imaging revealed demyelinating anterior visual pathway dysfunction and signs of extensive cervicothoracic transverse myelitis from the third cervical to lower thoracic vertebrae, respectively. Then a diagnosis of neuromyelitis optica was established. After treatment with high-dose systemic steroid followed by azathioprine, the patient was stable for several months with significant improvement of vision and lower-extremity weakness with no relapse of symptoms.ConclusionThe case described here is a rare inflammatory demyelinating disorder of the central nervous system occurring in East Africa. It reminds clinicians to suspect neuromyelitis optica in a patient who presented with unexplained recurrent optic neuritis to make a timely diagnosis and prevention of permanent neuronal damage. Neuromyelitis optica can also be associated with oculomotor nerve involvement.

Impairment of Visual Cognition in Progressive Multiple Sclerosis

Background: Impairment of visual cognition occurs in up to 25% of patients with MS, however data on progressive disease is limited and the neural basis remains unknown. Objective: To evaluate the influence of multifocal inflammatory CNS white matter demyelination burden on visual cognition in equivalent SPMS and PPMS cohorts. Methods: 59 SPMS and 27 PPMS patients matched for demographic and disease characteristics were evaluated using visuospatial and visuoperceptual components of the Addenbrooke’s cognitive examination-revised (ACE-R) battery. Factors influencing performance were then identified by logistic regression. Exploratory logistic models were also used to determine the predictive value of deficits in attention, working memory, and arithmetic abilities. Finally, comparison of deficits between equivalent primary (PPMS) and secondary (SPMS) progressive disease groups was used to evaluate a potential dose-response for cumulative multifocal inflammatory CNS white matter demyelination. Results: The overall prevalence of impairment in visual cognition was 14.0% (95%CI=6.4 to 21.4%) with no difference between disease groups. Qualitatively, the observed deficits in visual cognition were subtle, and patients were not able to predict them. Impairment was more common in women (OR 3.2; 95% CI=0.8 to 13.2), and subjects with a Beck depression inventory II score ≥ 25 (OR 5.2; 95% CI=1.1 to 24.2). No effect was seen for: age, years in full-time education, disease duration, clinical evidence of anterior visual pathway dysfunction, or motor disability. Exploratory analyses showed no predictive association with deficits in attention or working memory, however impairment of basic arithmetic skills was a highly significant predictor of impaired visual cognition (OR 29.4, 95% CI 3.0 to 291.9). Allowing for all significant predictors, secondary and primary progressive disease groups had equivalent rates of impairment (OR 1.6, 95% CI 0.4 to 7.1; p=0.538). Conclusions: Impairment of visual cognition in progressive MS is more common in women and patients with high levels of depressive symptomatology, but occurs independently from anterior visual pathway dysfunction and the cumulative burden of inflammatory CNS white matter demyelination. These findings suggest that the site rather than the absolute quantity of brain pathology is crucial, with the strong association observed to impairment of basic arithmetic skills implicating possible localization to the intraparietal sulcus.

Benign intermittent upbeat nystagmus in infancy: A new clinical entity

BackgroundUpbeat nystagmus in childhood is a rare phenomenon, which is classically associated with neurological or anterior visual pathway dysfunction. MethodsWe report a series of five infants with an intermittent upbeat nystagmus, without any other ocular or neurological abnormality, having spontaneously resolved before the age of 14 months. ResultsNystagmus beating frequency was between 1.5 and 2.5 Hz for all patients, amplitude was remarkably large due to a baseline position in downgaze. The nystagmus mostly occurred in supine position and could be triggered by head rotations in the supine position. Age of onset was from the first weeks of life to two months; age of resolution was 5–14 months. All infants underwent complete clinical examination with ophthalmological, oto-neurological and neurological assessments and MRI-scan. ConclusionsClinical characteristics of the nystagmus suggest an involvement of the otolithic system, with a secondary recalibration of the vestibulo-ocular pathways; however, no obvious vestibular abnormality was found. The pathophysiology of this nystagmus therefore remains unclear.

Cortical blindness

A 79-year-old woman with persistent cortical blindness caused by bilateral temporo-occipital infarctions was followed for 8 months. She had no light or visual motion perception. Our patient's visual imagery was intact, which was demonstrated when drawing elementary shapes; however, her drawing of objects was poor. Optokinetic nystagmus could not be elicited, but the vestibulo-ocular reflex (VOR) seemed intact. Although she was able to suppress her VOR by `fixating' her outstretched hand which moved in phase with her head and body, she showed saccadic tracking eye movements in an attempt to visually `follow' the self-generated movements of her outstretched hand, while her body and head were stationary. Such saccadic tracking seemed to be different from the previously described smooth tracking of self-moved targets by patients with acquired blindness caused by anterior visual pathway dysfunction.

Abstract

A 79-year-old woman with persistent cortical blindness caused by bilateral temporo-occipital infarctions was followed for 8 months. She had no light or visual motion perception. Our patient's visual imagery was intact, which was demonstrated when drawing elementary shapes; however, her drawing of objects was poor. Optokinetic nystagmus could not be elicited, but the vestibulo-ocular reflex (VOR) seemed intact. Although she was able to suppress her VOR by `fixating' her outstretched hand which moved in phase with her head and body, she showed saccadic tracking eye movements in an attempt to visually `follow' the self-generated movements of her outstretched hand, while her body and head were stationary. Such saccadic tracking seemed to be different from the previously described smooth tracking of self-moved targets by patients with acquired blindness caused by anterior visual pathway dysfunction.

The pattern electroretinogram in anterior visual pathway dysfunction and its relationship to the pattern visual evoked potential: a personal clinical review of 743 eyes.

The pattern electroretinogram (PERG) has now been in routine clinical use for sufficiently long to allow a personal clinical review of its relationship to the cortically generated pattern visual evoked potential (PVEP). The PERG and PVEP findings are presented from 520 eyes with optic nerve demyelination (382 eyes), optic nerve compression (90 eyes) or heredofamilial optic atrophy (48 eyes), and these are compared with the findings obtained in 223 eyes with dysfunction anterior to the retinal ganglion cells. Dysfunction anterior to the retinal ganglion cells gives a reduction in the P50 component of the PERG, but this component is usually spared in optic nerve disease where selective loss of the N95 component is by far the most frequently occurring abnormality. A diagnostic strategy is presented.

Lack of optokinetic nystagmus and visual motion perception in acquired cortical blindness

An 81-year-old man with persistent cortical blindness caused by bilateral temporo-occipital infarctions was followed for six months. He had no light or visual motion perception. Optokinetic stimulation did not elicit any optokinetic nystagmus (OKN), slow eye deviation responses, or circular vection, but the vestibulo-ocular reflex (VOR) was intact. Previously reported human cases of acquired cortical blindness with sufficient follow-up have shown similar features or otherwise either partial recovery of vision, OKN or slow eye deviation responses, or recovery of (subcortical?) OKN even without the recovery of vision and/or visual movement discrimination. It has been demonstrated that patients with acquired blindness due to anterior visual pathway dysfunction show the ability to generate smooth pursuit eye movements or to suppress the VOR by ‘tracking’ or ‘fixating’ their outstretched hand. Our patient was unable to do so. Preservation of subcortical OKN after ablation of the visual cortex is well-known in animal experiments (afoveate species, cat, and monkey). In monkeys, recovery of visual functions after cortical lesions seems to be be more rapid and more complete than in humans. This might be because monkeys can reorganize subcortical or extrastriate visual processing more successfully than humans and they are less reliant on cortical visual functions. For subcortical OKN in man, areas homologous to the MST and/or MT areas in the monkey are important, while for cortical OKN residual vision also seems necessary.

Pattern electroretinography in patients with delayed pattern visual evoked potentials due to distal anterior visual pathway dysfunction.

Between March 1983 and January 1988 delayed pattern visual evoked potentials (PVEP) were observed in 67 patients with distal visual pathway dysfunction. Many of these patients had been referred for neurophysiological examination because of possible optic nerve dysfunction. These patients also had pattern electroretinography (PERG) performed which in all cases showed an abnormality of the main positive P50 component. None of these patients had an abnormality confined to the negative N95 component, the type of abnormality usually found if the PERG is abnormal in optic nerve disease. It is suggested that PERG recording should now be a routine adjunct to the PVEP in the assessment of anterior visual pathway dysfunction.

Nystagmus and visual evoked potentials

The pattern reversal evoked potentials test (PR-VEP) is widely used for assessing the integrity of the anterior visual pathways. With the conventional black and white check stimulus, a successful test requires that the patient be able to fixate at the center of the screen. Although in most patients with nystagmus a reliable VEP can be obtained, we have noted that some patients may have no response even in the absence of anterior visual pathway dysfunction. We suspected that this was due to a decrease in foveation of each check, secondary to the nystagmus. To test this hypothesis we evaluated 4 patients with marked horizontal nystagmus and found no evidence of anterior visual pathway dysfunction. The conventional PR-VEP showed absence of P100 response bilaterally in all patients. With horizontal grating stimulus, two patients demonstrated well defined P100 responses bilaterally and in the other two, a unilateral response was noted. The latency and amplitude of all of these responses was normal. A study of six normal individuals (controls) with both checkerboard stimulus and horizontal grating revealed P100 responses with normal, comparable latencies. This data demonstrates the clinical usefulness of the horizontal grating technique in patients with marked nystagmus, in whom the conventional VEP has failed to register P100 component of the visual evoked test.

Compulsive thalamic self-stimulation: A case with metabolic, electrophysiologic and behavioral correlates

A 48-year-old woman with a stimulating electrode implanted in the right thalamic nucleus ventralis posterolateralis developed compulsive self-stimulation associated with erotic sensations and changes in autonomic and neurologic function. Stimulation effects were evaluated by neuropsychologic testing, endocrine studies, positron emission tomographic measurements of regional cerebral metabolic rate for glucose, EEG and evoked potentials. During stimulation, vital signs and pupillary diameter increased and a left hemiparesis and left hemisensory loss developed. Verbal functions deteriorated and visuospatial processing improved. Plasma growth hormone concentrations decreased, and adrenocorticotrophic hormone and cortisol levels rose. With stimulation, glucose metabolism increased in both thalami and both hemispheres, reversing baseline right-sided hypometabolism and right-left asymmetries. EEG and both somatosensory and brain-stem auditory evoked potentials remained unchanged during stimulation, while visual evoked potentials revealed evidence of anterior visual pathway dysfunction in the left eye. This case establishes the potential for addiction to deep brain stimulation and demonstrates that widespread behavioral and physiological changes, with concomitant alteration in the regional cerebral metabolic rate for glucose, may accompany unilateral thalamic stimulation.

Monocular pattern-shift visual evoked potentials in hemispheric strokes

Monocular pattern-shift visual evoked potentials were obtained in (i) 33 patients with unilateral non-hemorrhagic hemispheric infarction (age 50–79 years; 23 males, 10 females), (ii) 21 age- and sex-matched patient controls (control group or CGI) with no remote or recent stroke, normal neurological examination and similar incidence of diabetes mellitus, hypertension and heart disease, and (iii) 21 age- and sex-matched healthy elderly community volunteers (CGII). Subjects with history of glaucoma, cataracts, other media opacities or symptomatic retinal lesions were not considered or included in any of the 3 study groups. In addition, all subjects in each of the 3 groups had a normal ocular and fundoscopic examination. The mean interocular P100 latency difference in the stroke group was significantly greater than that in CGI or II ( P < 0.01). The mean interocular P100 amplitude ratio (small P100/large P100) in the stroke subjects was significantly different from that of CGI or II ( P < 0.02). The mean P100 latency on ocular stimulation ipsilateral to the side of infarction was significantly longer than that of either left or right ocular stimulation in CGI or II ( P < 0.01). The mean P100 latency on ocular stimulation contralateral to the side of infarction was similarly but less significantly longer than that on left or right ocular stimulation in CGI or II ( P < 0.05). Evidence of anterior visual pathway dysfunction was thus elicited in the stroke population using the technique.