Neuro-ophthalmological disorders in HIV infected subjects with neurological manifestations

AIMS

To determine the frequency and features of neuro-ophthalmological manifestations in neurologically symptomatic HIV infected patients and to assess whether or not the visual evoked potential (VEP) features in these patients differ from those of neurologically asymptomatic HIV infected patients.

METHODS

Neuro-ophthalmological evaluation was performed in 166 neurologically symptomatic confirmed HIV positive patients, of whom 75 with normal ophthalmological examination were further studied by means of VEPs. The VEPs values were compared to those obtained from 53 other confirmed HIV positive subjects with neither ophthalmological nor neurological manifestations, who served as a comparison group and to the references values of our laboratory.

RESULTS

An abnormal neuro-ophthalmological examination was noted in 99/166 patients (60%). Eye movement disorders were present in 99 patients (51%). Visual field defects were detected in 39% of the patients. Optic neuropathy was noted in 31%, papilloedema in 27% and ocular motor nerve palsies in 26% of the patients. Toxoplasmosis and cryptococcosis were the most frequent associated pathologies, though in some patients the HIV itself was the presumed cause. VEPs were abnormal in 57% and 42% of patients with and without neurological manifestations, respectively. Compared to asymptomatic patients, symptomatic patients had a significantly increased mean latency; however, both groups had significant increase in mean latency compared to reference values.

CONCLUSION

Neuro-ophthalmological manifestations are common in neurologically symptomatic HIV infected patients. Subclinical dysfunction in the visual pathways is a common phenomenon in both HIV infected patients with and without neurological symptoms, but neurologically symptomatic patients seem to have more damage in their visual pathways.

Optic chiasm enhancement associated with giant aneurysm and yttrium treated pituitary adenoma

A patient with a history of pituitary tumour treated with yttrium 29 years before presented with an asymmetrical chiasmal neuropathy. Magnetic resonance imaging showed a partially thrombosed giant aneurysm of the right internal carotid artery, with enhancement of the chiasm and right optic tract adjacent to the aneurysm. It was thought that, in addition to the effects of compression, a peri-aneurysmal inflammatory reaction had developed, causing breakdown of the blood-brain barrier and consequent inflammatory changes in the optic chiasm. High dose steroid treatment led to significant improvement in vision within two weeks. Steroids may have a role in the acute preservation of vision in similar cases, as well as in cases of deterioration following coiling or embolisation of aneurysms where thrombosis within the aneurysm has been induced.

Axonal degeneration and inflammation in acute optic neuritis

AIMS

To investigate whether plasma biomarkers for axonal injury and inflammation are related to loss and recovery of visual function in acute optic neuritis (ON).

METHODS

Eighteen patients with ON and 14 controls were investigated in a longitudinal, prospective study. Plasma phosphorylated neurofilament heavy chain (NfHSMI35; a surrogate marker of axonal injury), nitric oxide metabolites (NOx), and citrulline (surrogate markers of inflammation) were measured.

RESULTS

Patients with ON had higher median plasma NfHSMI35 values than controls (0.17 versus 0.005 ng/ml; p < 0.05) and higher NOx values (49 versus 35.5 microM; p < 0.001). Plasma NfHSMI35 values correlated inversely with visual acuity at presentation (R = -0.67; p = 0.01). NfHSMI35 was higher in patients with poor recovery of visual acuity than in those with good recovery (0.25 ng/ml versus 0.09 ng/ml; p < 0.05). Three of four patients with high NfHSMI35 and high NOx values experienced a poor recovery as opposed to only one of five with high NOx but normal NfH(SMI35) values.

CONCLUSIONS

NfHSMI35, a surrogate marker for axonal damage, is a prognostic indicator and should be considered in the design of neuroprotective treatment strategies.

Raised intracranial pressure presenting with spontaneous periorbital bruising: two case reports

The venous drainage of the orbit is known to be via the ophthalmic and vortex veins which communicate with the cavernous sinus. We describe two patients with raised intracranial pressure presenting with periorbital bruising. In one patient dural venous sinus thrombosis was demonstrated and it is suspected that the cause of the raised intracranial pressure may have been the same in the second. We suggest that the abrupt rise of pressure in the cerebral venous system was transmitted via the cavernous sinus to the orbital venous system.

Functional magnetic resonance imaging of the cerebral response to visual stimulation in medically unexplained visual loss

BACKGROUND

Medically unexplained visual loss occurs in 1 to 5% of patients attending ophthalmology clinics and for many it runs a chronic course. A psychogenic aetiology is presumed in such cases, but little is known about the underlying neural mechanisms. Recent studies have established the value of functional magnetic resonance imaging (fMRI) in understanding the mechanisms of unexplained motor and sensory symptoms. The purpose of this study was to use a similar strategy (fMRI) to evaluate the cerebral responses to visual stimulation in a group of patients with medically unexplained visual loss, in an attempt to determine the underlying neural mechanisms.

METHOD

Brain activation induced by periodic (monocular) 8 Hz visual stimulation was detected by fMRI in five patients with unexplained visual loss who fulfilled DSM-IV criteria for conversion disorder, and seven normal volunteers. Between-group differences in mean power of activation were estimated by fitting a one-way analysis of variance (ANOVA) model at each intracerebral voxel in standard space.

RESULTS

Compared with controls, patients showed reduced activation in visual cortices, but increased activation in left inferior frontal cortex, left insula-claustrum, bilateral striatum and thalami, left limbic structures, and left posterior cingulate cortex.

CONCLUSIONS

This preliminary study has identified novel neural correlates in patients with unexplained visual loss. The abnormal pattern of activation may reflect inhibition of primary visual cortex or a shift towards non-conscious (implicit) processing.

Elevated white matter myo-inositol in clinically isolated syndromes suggestive of multiple sclerosis

Normal-appearing white matter (NAWM) in established multiple sclerosis has been shown to be abnormal using a variety of magnetic resonance (MR) techniques, including proton MR spectroscopy ((1)H-MRS), although the stage at which these changes first appear is less clear. Using a 1.5 T scanner and single-voxel (1)H-MRS [TR 3000 ms, TE 30 ms, point-resolved spectroscopy (PRESS) localization], we determined NAWM metabolite concentrations in 96 patients a mean of 19 weeks (range 12-28 weeks) after onset of a clinically isolated syndrome (CIS) suggestive of multiple sclerosis and in 44 healthy control subjects. Absolute concentrations of N-acetyl-aspartate, total creatine and phosphocreatine (Cr), choline-containing compounds, glutamate plus glutamine, and myo-inositol (Ins) were estimated automatically using the LCModel. Compared with control subjects, the concentration of Ins was elevated in CIS NAWM (mean 3.31 mM, SD 0.86 versus mean 3.82 mM, SD 1.06; P = 0.001). The increase in Ins was also seen in the patient subgroup with abnormal T2-weighted MRI (mean 3.88 mM, SD 1.10; P = 0.001) and in those who satisfied the McDonald criteria for multiple sclerosis (mean 4.04 mM, SD 1.31; P = 0.001). An increase in Cr was also observed in CIS NAWM (P = 0.023), but other metabolites did not significantly differ between the whole CIS group and control subjects. There was no significant correlation between NAWM Ins and T2 lesion load. The early increase in Ins may reflect a process of pathogenic importance in multiple sclerosis NAWM. Follow-up studies will investigate whether the increase in NAWM Ins is of prognostic importance for future relapses and disability.

Serial magnetization transfer imaging in acute optic neuritis

In serial studies of multiple sclerosis lesions, reductions in magnetization transfer ratio (MTR) are thought to be due to demyelination and axonal loss, with later rises due to remyelination. This study followed serial changes in MTR in acute optic neuritis in combination with clinical and electrophysiological measurements to determine if the MTR changes over time mirror the picture in multiple sclerosis lesions, further validating MTR as a marker of tissue integrity. Twenty-nine patients were recruited who had acute optic neuritis for a median of 13 days (range 7-24 days) since the onset of visual symptoms. A clinical examination and measurement of visual evoked potentials (VEP) was performed on each patient. Their optic nerves were imaged with a fat-saturated fast spin echo (FSE) sequence and a magnetization transfer sequence. Twenty-one had multiple subsequent examinations over the course of 1 year. In addition, 27 control subjects had their optic nerves imaged up to three times over 1 year. A blinded observer segmented the optic nerves from the MTR maps. Lesions were defined on the acute FSE images and, from the coordinates, the ratio of mean lesion MTR : healthy nerve MTR (lesion ratio) was calculated for each dataset. The time-averaged mean MTR in control optic nerves was 47.7 per cent units (pu). In diseased optic nerves, baseline mean MTR was 47.3 pu, with a mean lesion ratio of 0.98. The diseased optic nerve MTR and lesion ratio declined over time with a nadir at about 240 days at a mean MTR value of 44.2 pu and mean lesion ratio of 0.91. Subsequently, diseased optic nerve MTR appeared to rise; after 1 year the diseased optic nerve mean MTR was 45.1 pu (mean lesion ratio 0.93), although the difference was not significant compared with the nadir value. For each 0.01 increase in time-averaged lesion ratio logMAR visual acuity recovery improved by 0.03 (95% CI, 0.002, 0.08, P = 0.02). Time-averaged VEP central field latency was shorter by 6.1 ms (95% CI 1.5, 10.7, P = 0.012) per 1 pu rise in time-averaged diseased optic nerve MTR. The early fall in diseased optic nerve MTR is consistent with demyelination and Wallerian degeneration of transected axons. The late nadir compared with studies of multiple sclerosis lesions may have been due to slow clearance of myelin debris. Remyelination may have influenced subsequent MTR changes. The observations support using MTR to monitor symptomatic demyelinating lesions.

[Treatment of optic neuritis]

Optic neuritis manifests itself as a reversible loss of vision. It can be a clinically isolated incident or one of the (first) manifestations of multiple sclerosis (MS). Its differential diagnosis is extensive, and management of other disorders can differ radically. In a typical case, treatment with corticosteroids hastens recovery of vision but does not affect the eventual degree of recovery. There is a substantial risk of developing MS after isolated optic neuritis (approximately 50% within 20 years), especially if asymptomatic white matter lesions are found on MRI scanning of the brain. Intravenous treatment with methylprednisolone may delay the onset of MS somewhat, but after three years the benefit of this treatment is lost. Treatment with interferon beta-Ia in high-risk patients also slows down the progression to clinically definite MS, but the long-term benefits are uncertain. MR imaging of the brain has implications for prognosis but not for treatment.

Spinal cord MRI in clinically isolated optic neuritis

BACKGROUND/METHODS

One hundred and fifteen patients with clinically isolated optic neuritis underwent magnetic resonance imaging (MRI) of the brain and spinal cord within 3 months of the onset of symptoms.

RESULTS

Eighty one (70%) patients had brain lesions and 31 (27%) had cord lesions. Cord lesions were seen in 12% with a normal brain MRI, 21% with between one and eight brain lesions, and 45% with nine or more brain lesions. When the new diagnostic criteria for MS were applied, MRI cord imaging used for evidence of dissemination in time and space allowed a diagnosis of MS in only one additional asymptomatic patient at 1 year, two additional asymptomatic patients at 3 years.

CONCLUSIONS

Using existing criteria, spinal cord imaging rarely contributes to the diagnosis in patients with clinically isolated optic neuritis.

Visual Evoked Potentials in Konzo, a Spastic Paraparesis of Acute Onset in Africa

AIM

To assess whether or not visual evoked potentials (VEPs) are abnormal in konzo, a para/tetraparesis of sudden onset, and to correlate the findings to the clinical picture of the disorder.

METHODS

VEPs were recorded in 23 patients (9 men and 14 women, mean age: 23 +/- 10 years) suffering from konzo, and 38 healthy subjects (20 men and 18 women, mean age: 27 +/- 15 years). The mean P100 latencies and peak-to-peak N75-P100 amplitudes of each eye were measured and compared in the two groups. The mean interocular P100 latency and amplitude differences were calculated and also compared.

RESULTS

VEPs were abnormal in 11/23 patients (48%) consisting of P100 prolongation (7 subjects), absence of P100 wave (2 subjects) or an atypical waveform (2 subjects). The mean P100 latency value of the konzo group was significantly increased as compared with the mean (+ 2.5 SD) of the reference values from healthy subjects (p < 0.05). There was a statistically significant decrease of amplitude in konzo patients compared to normal subjects (p < 0.05) with, however, only 2 patients outside the 95% confidence limits. Six patients (27%) had abnormal VEPs despite normal visual acuity. These abnormalities were symmetric and a relation could be found between neither the duration nor the severity of the disease and the VEP perturbation.

CONCLUSION

The main features of these abnormalities are delayed P100 latency and decreased amplitude. These findings indicate involvement of visual pathways and seem to suggest the presence of axonal loss in the prechiasmal visual pathways in konzo. This study provides evidence that the neurodamage in konzo extends to the visual pathways.

"Bottom-up" and "top-down" effects on reading saccades: a case study

OBJECTIVE

To investigate the role right foveal/parafoveal sparing plays in reading single words, word arrays, and eye movement patterns in a single case with an incongruous hemianopia.

METHODS

The patient, a 48-year-old right handed male with a macular sparing hemianopia in his left eye and a macular splitting hemianopia in his right eye, performed various reading tasks. Single word reading speeds were monitored using a "voice-trigger" system. Eye movements were recorded while reading three passages of text, and PET data were gathered while the subject performed a variety of reading tasks in the camera.

RESULTS

The patient was faster at reading single words and text with his left eye compared with his right. A small word length effect was present in his right eye but not his left. His eye movement patterns were more orderly when reading text with his left eye, making fewer saccades. The PET data provided evidence of "top-down" processes involved in reading. Binocular single word reading produced activity in the representation of foveal V1 bilaterally; however, text reading with the left eye only was associated with activation in left but not right parafoveal V1, despite there being visual stimuli in both visual fields.

CONCLUSIONS

The presence of a word length effect (typically associated with pure alexia) can be caused by a macular splitting hemianopia. Right parafoveal vision is not critically involved in single word identification, but is when planning left to right reading saccades. The influence of top-down attentional processes during text reading can be visualised in parafoveal V1 using PET.

Giant cell arteritis mimicking idiopathic orbital inflammatory disease

PURPOSE

To report an unusual presentation of giant cell arteritis, referred from primary care, mimicking orbital apex syndrome.

CASE REPORT

A 72 year old woman was referred with a two week history of pyrexia, dull right eye ache, 2mm of right proptosis, mild conjunctival chemosis and restriction of right eye movements.

RESULTS

An erythrocyte sedimentation rate (ESR) was 90 and fluorescein angiography showed almost complete choroidal non-perfusion suggestive of giant cell arteritis. Temporal artery biopsy confirmed the diagnosis.

CONCLUSIONS

Giant cell arteritis (GCA) typically presents with anterior ischemic optic neuropathy (AION), choroidal ischemia, central retinal artery occlusion, infrequently manifesting as an ocular motility problem, but has rarely been known to mimick idiopathic orbital inflammatory disease. Prompt recognition and therapy can minimize the chance of ipsilateral ocular involvement and protect the fellow eye.

Chronic relapsing inflammatory optic neuropathy (CRION)

We describe the clinical characteristics and early natural history of a form of inflammatory optic neuropathy which is frequently bilateral and often painful, and is characterized by relapses and remissions. MRI scans of the brain are normal and those of the optic nerves often, but not always, show high signal abnormalities which enhance. The symptoms and signs respond well to corticosteroid treatment, although long-term immuno suppression is often necessary. The syndrome behaves in a way which is typical of the condition known as granulomatous optic neuropathy, but during a median follow-up of 8 (2-26) years in no case has evidence for systemic sarcoidosis been identified. We suggest that the disorder be named chronic relapsing inflammatory optic neuropathy (CRION).

Management of acute optic neuritis

Optic neuritis is a common condition that causes reversible loss of vision. It can be clinically isolated or can arise as one of the manifestations of multiple sclerosis. Occasional cases are due to other causes, and in these instances management can differ radically. The treatment of optic neuritis has been investigated in several trials, the results of which have shown that corticosteroids speed up the recovery of vision without affecting the final visual outcome. Other aspects of management, however, are controversial, and there is uncertainty about when to investigate and when to treat the condition. Here we review the diagnostic features of optic neuritis, its differential diagnosis, and give practical guidance about management of patients. The condition's association with multiple sclerosis will be considered in the light of studies that define the risk for development of multiple sclerosis and with respect to results of trials of disease-modifying drugs in these individuals.

Functional magnetic resonance imaging of the cortical response to photic stimulation in humans following optic neuritis recovery

Recovery from optic neuritis has been shown to be associated with an abnormal functional MRI (fMRI) response following exposure of the eye to an epoch based (ON-OFF design) flickering photic stimulus. Visual cortex activation is reduced during photic stimulation, whilst extra-occipital areas are extensively activated with a peak blood oxygen level dependent response during the OFF phase of the stimulus paradigm. We performed a further fMRI experiment to determine whether the abnormal extra-occipital response is a phase-specific phenomenon or whether it results from a delayed haemodynamic response. A cohort of patients that recovered from optic neuritis was studied, this time using a longer photic stimulation epoch (40 s). The extra-occipital response again peaked during the baseline condition, indicating that the phenomenon is phase dependent. Our results also reinforce the important findings of extra-occipital activation following optic neuritis which may represent an adaptive reorganization of the cerebral response.

Ladies with Leber's hereditary optic neuropathy: an atypical disease

PURPOSE

Leber's Hereditary Optic Neuropathy (LHON) is considered to be a disease predominantly affecting young males. The risk of women becoming symptomatic if they are carriers of a primary mutation is 1/5 of that in males. The disease however appears to behave differently in women in some instances. We describe three cases of ladies with LHON and discuss the importance of making the diagnosis.

CASE REPORTS

A 28-year-old female presented with blurring of vision in her left eye with bilateral small hyperemic discs and telangiectatic vessels adjacent to them. DNA analysis confirmed the 11778 mutation and the second eye remains unaffected 10 years later. The second case was 49 years old and presented with bilateral visual loss developing over 3 months. She had no family history of visual loss but had a past history of Wolf Parkinson White syndrome and 3460 mutation was confirmed. The last case was diagnosed with multiple sclerosis at age 24 and went on to develop visual loss with poor recovery. DNA analysis demonstrated the 11778 mutation and confirmed LHON.

CONCLUSIONS

All three cases, although not unique, posed considerable diagnostic difficulties over a long period of time. The authors have highlighted important associations of the disease and stress the importance of making the diagnosis in women. They are at increased risk of having affected children, unlike the affected males, especially if they are affected themselves and may wish to seek further genetic advice.

Progressive ventricular enlargement in patients with clinically isolated syndromes is associated with the early development of multiple sclerosis

BACKGROUND

In patients with clinically isolated syndromes (CIS) suggestive of multiple sclerosis (MS), the extent of brain magnetic resonance imaging (MRI) lesion load influences the probability and time to development of clinically definite MS. Cerebral atrophy is recognised in established MS, but its time of onset and whether, in early disease, it is related to MRI lesion load or clinical outcome is less certain.

OBJECTIVES

This study investigated ventricular enlargement over one year in CIS patients and explored its relation with lesion load and clinical outcome.

METHODS

A semi-automated thresholding technique for measuring ventricular volume (MIDAS) was applied to MRI scans in a cohort of 55 patients with CIS, recruited consecutively and imaged within three months of the onset of symptoms and again after one year.

RESULTS

Clinical MS had developed after one year in 16 of 40 patients with an abnormal baseline T2 scan and 2 of 15 with a normal scan. Significant ventricular enlargement was seen in 27 of 55 patients who fulfilled the new McDonald MRI criteria for MS using all available MRI at clinical follow up (median increase 0.3 cm(3), p=0.005) Significant increase in ventricular volume was also seen in the 18 of 55 patients who developed clinical MS over the follow up period (median increase 0.5 cm(3), p=0.006). There were significant but modest correlations between baseline lesion measures and subsequent ventricular enlargement.

CONCLUSIONS

(1) Lesions and atrophy are both associated with early relapse leading to a diagnosis of clinical MS; (2) while lesions contribute to the development of atrophy, atrophy may also develop by other mechanisms. This suggests that MR measures have a complementary role in monitoring the course of MS, even from the earliest clinical stage.

Normal-appearing brain tissue MTR histograms in clinically isolated syndromes suggestive of MS

Segmented normal-appearing brain tissue (NABT) was investigated in 40 patients with a recent onset and 13 patients with a remote onset of a clinically isolated syndrome (CIS) using magnetization transfer ratio (MTR) histograms. Abnormalities were present in patients with a high risk for MS (recent onset and T2-weighted lesions present) and in those with a low risk for relapse (recent onset without T2-weighted lesions). Similar mild NABT abnormality was present with CIS and no further disease activity 14 years later. NABT MTR abnormality in CIS may indicate susceptibility to demyelination but not to disease progression.

Ataxia in the setting of complicated enteropathy: double jeopardy

The differential diagnosis of subacute onset ataxia in the setting of enteropathy is wide. A 54 year old patient with a pancerebellar syndrome and known ulcerative jejunoileitis is described. Small bowel biopsy showed evidence of enteropathy associated T cell lymphoma and subsequent neuropathological analysis and immunophenotyping confirmed metastasis of this tumour to the cerebellum. The presence of anti-gliadin antibodies and MRI evidence of a more longstanding process suggested additional immunologically mediated cerebellar dysfunction. Lymphomatous involvement of the CNS is rare in patients with complicated enteropathies, and has not been previously reported to involve the cerebellar parenchyma. This diagnostic possibility should be borne in mind before attributing cerebellar dysfunction in patients with the coeliac related enteropathies to nutritional compromise or immunological dysfunction (gluten ataxia) alone.

B Cell lymphoma of the brain stem masquerading as myasthenia

A 54 year old man is described with signs compatible with ocular myasthenia gravis and an apparent excellent response to pyridostigmine. Subsequent clinical progression and further investigation suggested the presence of an inflammatory brain stem lesion, which responded to corticosteroid therapy. Clinical relapse, including the development of central neurogenic hyperventilation, led to a brain stem biopsy, confirming a diagnosis of B cell lymphoma. This case illustrates the propensity of primary CNS lymphoma (PCNSL) to mimic other conditions. Brain MRI is mandatory in presumed "test negative" ocular myasthenia with atypical clinical findings. Spontaneous regression of PCNSL or response to corticosteroids is common and should not mitigate against the diagnosis. Histopathological confirmation should ideally be made before starting therapy, as this may obscure or delay the correct diagnosis. Although PCNSL is rare, it must be considered in all patients with brain stem syndromes, and in all patients 50 years or older with contrast enhancing focal lesions.