Diaschisis: past, present, future

Abstract

After a century of false hopes, recent studies have placed the concept of diaschisis at the centre of the understanding of brain function. Originally, the term 'diaschisis' was coined by von Monakow in 1914 to describe the neurophysiological changes that occur distant to a focal brain lesion. In the following decades, this concept triggered widespread clinical interest in an attempt to describe symptoms and signs that the lesion could not fully explain. However, the first imaging studies, in the late 1970s, only partially confirmed the clinical significance of diaschisis. Focal cortical areas of diaschisis (i.e. focal diaschisis) contributed to the clinical deficits after subcortical but only rarely after cortical lesions. For this reason, the concept of diaschisis progressively disappeared from the mainstream of research in clinical neurosciences. Recent evidence has unexpectedly revitalized the notion. The development of new imaging techniques allows a better understanding of the complexity of brain organization. It is now possible to reliably investigate a new type of diaschisis defined as the changes of structural and functional connectivity between brain areas distant to the lesion (i.e. connectional diaschisis). As opposed to focal diaschisis, connectional diaschisis, focusing on determined networks, seems to relate more consistently to the clinical findings. This is particularly true after stroke in the motor and attentional networks. Furthermore, normalization of remote connectivity changes in these networks relates to a better recovery. In the future, to investigate the clinical role of diaschisis, a systematic approach has to be considered. First, emerging imaging and electrophysiological techniques should be used to precisely map and selectively model brain lesions in human and animals studies. Second, the concept of diaschisis must be applied to determine the impact of a focal lesion on new representations of the complexity of brain organization. As an example, the evaluation of remote changes in the structure of the connectome has so far mainly been tested by modelization of focal brain lesions. These changes could now be assessed in patients suffering from focal brain lesions (i.e. connectomal diaschisis). Finally, and of major significance, focal and non-focal neurophysiological changes distant to the lesion should be the target of therapeutic strategies. Neuromodulation using transcranial magnetic stimulation is one of the most promising techniques. It is when this last step will be successful that the concept of diaschisis will gain all the clinical respectability that could not be obtained in decades of research.

The 3 Rs of Stroke Biology: Radial, Relayed, and Regenerative

“…Diaschisis in its original, definitional form refers to electrical dysfunction remote from a focal lesion. It later came to mean metabolic dysfunction or a reduction in blood flow in remote brain areas after a single focal stroke [83,84]. Recent network analyses in human and animal models of stroke have shown widespread disconnection of functional brain networks with stroke.…”

“…These disruptions in neuronal networks by stroke occur in regions in which metabolic or blood flow changes have not been reported in focal stroke. Recent attempts to reconcile the historical concept of diaschisis with newer findings that many, many brain areas are disconnected by stroke has led to the awkward expansion of this term into Bfocal diaschisis^, Bconnectional diaschisis^, and Bconnectomal diaschisis^ [84].…”

“…At its heart and in the original coining of the term, diaschisis was used to explain why focal stroke could produce behavioral deficits not associated with the location of the stroke [83,84]. In recent studies of widespread neuronal network alterations after single strokes, behavioral deficits occur as a result of loss of connections between brain areas in many patterns, which are far more diverse in their connectivity than could be explained by known patterns of diaschisis [86].…”

Structural and Functional Neuroimaging in the Investigation of the Brain Neuroplasticity in Post-Stroke Patients (Literature Review)

“…Например, степень повреждения кортикального спинного тракта (КСТ) коррелирует с двигательной способностью у по-стинсультных больных [14]. Однако повреждение, связанное с инсультом, также оказывает влияние на районы, удаленные от места поражения [15]. Кроме того, время оценки состояния мозга после инсульта также является важным в связи с развитием отсроченной атрофии в областях, уда-ленных от места поражения [16].…”

Neurorehabilitation in Multiple Sclerosis – Resilience in Practice

“…This proposal was highly prescient and was confirmed by imaging and electrophysiological studies almost a century later. [10][11][12] Neuroplasticity involves functional adaptations that occur at various different levels in MS. [13][14][15][16][17] At the cellular level, changes include axonal sprouting (increased arborisation of neurones), changes of synaptic stability and reorganisation of synapses. At the tissue level, there is resorption of oedema and rearrangement of Na-channels on axons beyond the nodes of Ranvier.…”