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Transorbital alternating current stimulation modifies BOLD activity in healthy subjects and in a stroke patient with hemianopia: A 7 Tesla fMRI feasibility study

Sabel BA, Hamid AIA, Borrmann C, Speck O, Antal A

Int J Psychophysiol, 2020 08;154:80-92.
PMID: 30978369 DOI: 10.1016/j.ijpsycho.2019.04.002

BACKGROUND: Modifying brain activity using non-invasive, low intensity transcranial electrical brain stimulation (TES) has rapidly increased during the past 20 years. Alternating current stimulation (ACS), for example, has been shown to alter brain rhythm activities and modify neuronal functioning in the visual system. Daily application of transorbital ACS to patients with optic nerve damage induces functional connectivity reorganization, and partially restores vision. While ACS is thought to mainly modify neuronal mechanisms, e.g. changes in brain oscillations that can be detected by EEG, it is still an open question, whether and how it may alter BOLD activity.
OBJECTIVE: We evaluated whether transorbital ACS modulates BOLD activity in early visual cortex using high-resolution 7 Tesla functional magnetic resonance imaging (fMRI).
METHODS: In this feasibility study transorbital ACS in the alpha range and sham ACS was applied in a random block design in five healthy subjects for 20 min at 1 mA. Brain activation in the visual areas V1, V2 and V3 were measured using 7 Tesla fMRI-based retinotopic mapping at the time points before (baseline) and after stimulation. In addition, we collected data from one hemianopic stroke patient with visual cortex damage after ten daily sessions with 25-50 min stimulation duration.
RESULTS: In healthy subjects transorbital ACS increased the activated cortical surface area, decreased the fMRI response amplitude and increased coherence in the visual cortex, which was most prominent in the full field task. In the patient, stimulation improved contrast sensitivity in the central visual field. BOLD amplitudes and coherence values were increased in most early visual areas in both hemispheres, with the most pronounced activation detected during eccentricity testing in retinotopic mapping.
CONCLUSIONS: This feasibility study showed that transorbital ACS modifies BOLD activity to visual stimulation, which outlasts the duration of the AC stimulation. This is in line with earlier neurophysiological findings of increased power in EEG recordings and functional connectivity reorganization in patients with impaired vision. Accordingly, the larger BOLD response area after stimulation can be explained by more coherent activation and lower variability in the activation. Alternatively, increased neuronal activity can also be taken into account. Controlled trials are needed to systematically evaluate the potential of repetitive transorbital ACS to improve visual function after visual pathway stroke and to determine the cause-effect relationship between neural and BOLD activity changes.

Matched MeSH terms: Hemianopsia*
Fulltext Unilateral neglect or alien hand syndrome? A diagnostic challenge

Wan Yusoff WR, Hanafi MH, Ibrahim AH, Kassim NK, Suhaimi A

J Taibah Univ Med Sci, 2021 Apr;16(2):288-291.
PMID: 33897336 DOI: 10.1016/j.jtumed.2020.12.003

Alien hand syndrome (AHS) is a rare post-stroke complication. Although the occurrence of AHS after stroke is rare, it can have a disabling impact on the lifestyle and career of the patients post stroke. It is difficult to distinguish AHS from the non-dominant hemispheric infarction with symptoms of hemianopia and left hemineglect, as patients with AHS can also have neglect as well as behaviour symptoms if the frontal lobe is involved. We report the case of a 62-year-old gentleman who was admitted to the rehabilitation ward and was treated for neglect and apraxia following right middle cerebral artery stroke. After further re-evaluation, the patient was diagnosed with AHS. Functionally, he improved and the symptoms disappeared four months after the stroke. In this case report, we highlight the features of AHS and provide a unique management approach.

Matched MeSH terms: Hemianopsia
Fulltext Homonymous Hemianopia: A Rare Presentation of Secondary Central Nervous System Neurolymphomatosis

Awis Qarni F, Tai E, Wh WH, Husin A

Cureus, 2018 May 29;10(5):e2708.
PMID: 30062082 DOI: 10.7759/cureus.2708

Neurolymphomatosis is an atypical complication of non-Hodgkin lymphoma and leukaemia involving infiltration of neurotropic neoplastic cells in the central or peripheral nervous system. A 28-year-old Malay lady with background diffuse large B-cell lymphoma stage IV presented with left homonymous hemianopia associated with cognitive function deterioration. Her best corrected visual acuity was 6/9 in both eyes. Magnetic resonance imaging (MRI) of the brain showed a lesion suggestive of secondary lymphomatous infiltration of the splenium of corpus callosum. The patient underwent chemotherapy, after which repeated MRI showed a reduction in the lesion size. Homonymous hemianopia is a rare presentation of secondary central nervous system neurolymphomatosis. A comprehensive history, physical examination, and radiological imaging are essential to establish the diagnosis in patients presenting with visual field defects.

Matched MeSH terms: Hemianopsia
Fulltext Occipital Falcine Anaplastic Hemangiopericytoma Mimicking Meningioma

Kanesen D, Kandasamy R, Idris Z

J Neurosci Rural Pract, 2016 Dec;7(Suppl 1):S95-S98.
PMID: 28163517 DOI: 10.4103/0976-3147.196463

The rarity of hemangiopericytoma (HPC) and its controversial histological classification result in its frequent misdiagnosis and thus make the treatment quite challenging. It is often difficult to distinguish these tumors from meningiomas based on clinical features and radiological findings. This is a case report of a man, diagnosed clinically and radiologically as meningioma, which turned out to be anaplastic HPC on histological examination. A 30-year-old man presented with 3 months of progressively worsening of headache and blurring of vision. Clinical examination revealed the right homonymous hemianopia with reduced visual acuity and papilledema bilaterally. Magnetic resonance imaging revealed a multilobulated and heterogenous extraaxial lesion attached to the occipital falx. It measured 9.0 cm (AP) × 5.5 cm (W) × 5.8 cm (CC) and expands bilaterally with major bulk on the left. An occipital craniotomy followed by a subtotal tumor excision was only achieved due to profuse bleeding intraoperatively. Histopathology confirmed an anaplastic HPC (WHO Grade 3). The importance of differentiation between HPCs and meningiomas cannot be overemphasized. A preoperative correct diagnosis is difficult, but it is important that it should be made. Multilobulated (mushroom appearance), prominent internal signal voids, relatively narrow dural attachment, and lytic destruction without calcifications are useful findings to distinguish HPCs from meningiomas.

Matched MeSH terms: Hemianopsia