Tremor pathophysiology
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Zehra Malik, M.B.B.S[2]
Overview
It is thought that tremor is the result of a combination of different mechanisms that could result in oscillatory/rhythmic movement. These mechanisms are mechanical oscillations, reflex oscillations, central oscillations, and cerebellar oscillation. These mechanisms differ on the basis of their origin.
Pathophysiology
Physiology
The normal physiology of tremor is based on the four oscillatory centers: [1][2][3]
- Mechanical oscillations: Occurs in limbs, could be limited to a particular joint
- Reflex oscillations: Originates from afferent muscle spindles
- Central neuronal pacemaker: Involves thalamus, basal ganglia, inferior olive.
- Cerebellar Oscillations: Disturbance in feedforward or feedback loops in cerebellum resulting in oscillations.
Pathogenesis
- It is understood that tremor is the result of oscillations produced by the above-mentioned mechanisms.
- Following are some common causes of tremor and the mechanisms they originate from: [1]
| Common Causes of Tremor | Predominant Mechanism |
| Physiological tremor | Mechanical and central |
| Psychogenic tremor | Reflex (clonus) |
| Symptomatic palatal tremor | Central (inferior olive) |
| Essential tremor | Central and cerebellar (olivocerebellar circuits) |
| Parkinson's disease | Central (basal ganglia) |
| Toxic and drug‐induced tremors | Reflex |
Genetics
- Essential tremor is transmitted in an autosomal dominant pattern. So far, no particular genes have been identified as the cause. In Linkage study, three susceptible loci were mapped in families with pure monogenic essential tremor: [4]
- 3q13
- 2p25-p22
- 6p23
- Wilson's disease is transmitted in an autosomal recessive pattern. [5]
- Mutation in the ATP7B gene on chromosome 13 (13q14.3)
Associated Conditions
Conditions associated with tremor include:
- Parkinson's disease
- Drug-induced parkinsonism:Neuroleptics, metaclopromide,phenothiazines
- Wilson's disease
- Metabolic disorders: Thyrotoxicosis, pheochromocytoma, hypoglycemia
- Alcohol withdrawal
- Peripheral Neuropathy
- Orthostatic tremor
- Essential tremor
Gross Pathology
On gross pathology, Parkinson's disease has loss of dopamine pigment in the substantia nigra.
Microscopic Pathology
On microscopic histopathological analysis, Lewy bodies and Lewy neurites are found in neuronal cell bodies and neuronal cell processes, respectively in patients with Parkinson's disease.
References
- ↑ 1.0 1.1 Deuschl G, Raethjen J, Lindemann M, Krack P (2001). "The pathophysiology of tremor". Muscle Nerve. 24 (6): 716–35. doi:10.1002/mus.1063. PMID 11360255.
- ↑ Deuschl G, Krack P, Lauk M, Timmer J (1996). "Clinical neurophysiology of tremor". J Clin Neurophysiol. 13 (2): 110–21. doi:10.1097/00004691-199603000-00002. PMID 8849966.
- ↑ Elble RJ (1996). "Central mechanisms of tremor". J Clin Neurophysiol. 13 (2): 133–44. doi:10.1097/00004691-199603000-00004. PMID 8849968.
- ↑ Jiménez-Jiménez FJ, Alonso-Navarro H, García-Martín E, Lorenzo-Betancor O, Pastor P, Agúndez JA (2013). "Update on genetics of essential tremor". Acta Neurol Scand. 128 (6): 359–71. doi:10.1111/ane.12148. PMID 23682623.
- ↑ Ala A, Walker AP, Ashkan K, Dooley JS, Schilsky ML (2007). "Wilson's disease". Lancet. 369 (9559): 397–408. doi:10.1016/S0140-6736(07)60196-2. PMID 17276780.