Transient global amneisa causes
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Hasnain Ali Moryani, MBBS.
Overview
The cause of transient global amnesia is still uncertain.
Most evidence favors atypical vascular/ischemic mechanisms in medial temporal structures, with delayed hippocampal MRI lesions and bitemporal hypoperfusion.
Migraine phenomena, venous congestion, and angiography-triggered episodes suggest possible vascular or cortical irritation mechanisms, but none are proven.
Causes
- No adequate pathophysiological explanation of transient global amnesia has emerged.
- Early theories that attributed episodes to seizures are not supported by electroencephalographic and other techniques.
- Most current premises involve unconventional vascular or ischemic mechanisms affecting the medial temporal lobes, thalamus, or the posterior cerebral circulation that supplies these regions.[1] [2]
- A minimally higher risk of future stroke was suggested in one large propensity-matched analysis, but other series did not show an increased risk of subsequent ischemic stroke.[3] [2] [4]
- The delayed appearance of small lesions on diffusion-weighted MRI in the hippocampus and adjacent structures provides tentative support for a vascular mechanism, but it is unknown why these lesions are delayed or whether they reflect ischemia or altered neuronal physiology.[5]
- Functional imaging has shown bitemporal hypoperfusion during episodes.[6]
- Studies of neural networks during episodes demonstrate reduced connectivity of the hippocampi and parahippocampal gyri bilaterally, and reduced connectivity of other structures (such as the amygdala and portions of the lateral temporal lobe), confirming that the hippocampus is a nexus of memory formation and retrieval.[7]
- Migraine offers a possible link through cortical spreading depression (a wave of depolarization followed by suppression of neural activity and hypoperfusion) as a plausible mechanism, but the trigger is unknown and the evidence is circumstantial.[8] [1]
- A venous reflux mechanism with vascular congestion of the temporal lobes has been proposed, based on retrograde blood flow in the jugular veins during the Valsalva maneuver and incompetent jugular venous valves, but these hypotheses have not been confirmed.[9] [10]
- Episodes occurring immediately after angiographic injection of dye into a vertebral artery support a vascular mechanism or cortical irritation in a way that is similar to migraine phenomena.[1]
References
- ↑ 1.0 1.1 1.2 Bartsch T, Deuschl G (February 2010). "Transient global amnesia: functional anatomy and clinical implications". Lancet Neurol. 9 (2): 205–14. doi:10.1016/S1474-4422(09)70344-8. PMID 20129169.
- ↑ 2.0 2.1 Mangla A, Navi BB, Layton K, Kamel H (February 2014). "Transient global amnesia and the risk of ischemic stroke". Stroke. 45 (2): 389–93. doi:10.1161/STROKEAHA.113.003916. PMC 3946840. PMID 24309586.
- ↑ Zorzon M, Antonutti L, Masè G, Biasutti E, Vitrani B, Cazzato G (September 1995). "Transient global amnesia and transient ischemic attack. Natural history, vascular risk factors, and associated conditions". Stroke. 26 (9): 1536–42. doi:10.1161/01.str.26.9.1536. PMID 7660394.
- ↑ Lee SH, Kim KY, Lee JW, Park SJ, Jung JM (April 2022). "Risk of ischaemic stroke in patients with transient global amnesia: a propensity-matched cohort study". Stroke Vasc Neurol. 7 (2): 101–107. doi:10.1136/svn-2021-001006. PMC 9067272 Check
|pmc=value (help). PMID 34702748 Check|pmid=value (help). - ↑ Kim J, Kim Y (October 2022). "Distorted time perception in patients with transient global amnesia: time perception task and imaging analysis". Neurol Sci. 43 (10): 5951–5958. doi:10.1007/s10072-022-06219-0. PMID 35849197 Check
|pmid=value (help). - ↑ Stillhard G, Landis T, Schiess R, Regard M, Sialer G (April 1990). "Bitemporal hypoperfusion in transient global amnesia: 99m-Tc-HM-PAO SPECT and neuropsychological findings during and after an attack". J Neurol Neurosurg Psychiatry. 53 (4): 339–42. doi:10.1136/jnnp.53.4.339. PMC 1014174. PMID 2341849.
- ↑ Peer M, Nitzan M, Goldberg I, Katz J, Gomori JM, Ben-Hur T, Arzy S (May 2014). "Reversible functional connectivity disturbances during transient global amnesia". Ann Neurol. 75 (5): 634–43. doi:10.1002/ana.24137. PMID 24623317.
- ↑ Liampas I, Siouras AS, Siokas V, Tsouris Z, Rikos D, Brotis A, Aloizou AM, Dastamani M, Dardiotis E (January 2022). "Migraine in transient global amnesia: a meta-analysis of observational studies". J Neurol. 269 (1): 184–196. doi:10.1007/s00415-020-10363-y. PMID 33388926 Check
|pmid=value (help). - ↑ Sander D, Winbeck K, Etgen T, Knapp R, Klingelhöfer J, Conrad B (December 2000). "Disturbance of venous flow patterns in patients with transient global amnesia". Lancet. 356 (9246): 1982–4. doi:10.1016/S0140-6736(00)03313-4. PMID 11130530.
- ↑ Schreiber SJ, Doepp F, Klingebiel R, Valdueza JM (April 2005). "Internal jugular vein valve incompetence and intracranial venous anatomy in transient global amnesia". J Neurol Neurosurg Psychiatry. 76 (4): 509–13. doi:10.1136/jnnp.2004.043844. PMC 1739578. PMID 15774436.