Causes edit
Intention tremors have a variety of recorded causes. Anything that negatively impacts the cerebellum, brainstem, or thalamus has the potential to induce intention tremors. Some cause include a variety of neurological disorders, such as Multiple Sclerosis, Stroke, Alcoholism, Alcohol withdrawal, Peripheral neuropathy, Wilson's Disease and Fragile X Syndrome, as well as Brain tumors, low blood sugar, normal aging, a variety of drugs, such as sedatives and anticonvulsants, and traumatic brain injury.[1][2][3][4] There has also been a connection of intention tremors to viruses, such as West Nile Virus.[5] A variety of poisons have also been shown to cause intention tremors, including mercury, methyl bromide, phosphine, and lithium.[6][7][3] Vitamin deficiencies have also been linked to intention tremors, especially deficiency in Vitamin E.[8] Some normal everyday activities have also been shown to cause intention tremors, including ingesting too much caffeine, cigarettes, stress, anxiety, fear, anger and fatigue.[1]
Mechanism edit
Intention tremors caused by common causes such as stress, anxiety, fear, anger, caffeine, and fatigue do not seem to result from damage to any part of the brain. These tremors instead seem to be a temporary worsening of a small tremor that is present in every human being. These tremors go away with time.[1]
More permanent intention tremors are caused by damage to certain regions of the brain. The most common cause for intention tremors is damage to the cerebellum. The cerebellum is a part of the brain responsible for motor coordination, posture and balance. It is responsible for fine motor movements. When the cerebellum is damaged, a person has difficulty executing a fine motor movement, such as attempting to touch one's nose with one's finger. One of the most common ways for the cerebellum to become damaged is through the development of cerebellar lesions.[9] The most common site for cerebellar lesions that lead to intention tremors have been reported to be the superior cerebellar peduncle, through which all fibers carrying information to the midbrain pass, and the dentate nucleus, which is also responsible for linking the cerebellum to the rest of the brain.[10] A common example of this is the effect of alcohol abuse on the cerebellum. The alcohol abuse causes degeneration of the anterior vermis of the cerebellum. This leads to an inability to process fine motor movements in the patient and the development of intention tremors. In Multiple Sclerosis, damage occurs due to demyelination and neuron death, which again produces cerebellar lesions and an inability for those neurons to transmit signals. [9] Because of this tight association with damage to the cerebellum, intention tremors are often referred to as cerebellar tremors.[3]
Intention tremors can also be caused as a result of damage to the brainstem or thalamus. Both of these structures are involved in the transmission of information between the cerebellum and the cerebral cortex, as well as between the cerebellum and the spinal cord and then on to the motor neurons. When these become damaged, the relay system between between the cerebellum and the muscle on which it is try to act upon is compromised, thus resulting in the development of a tremor.[9]
References edit
- ^ a b c [1] Hoch, Daniel MD. “Tremor.” Updated 6/15/2010. U.S. National Library of Medicine.
- ^ [2] Hagerman, Paul, Hagerman, Randi. “Fragile X-Associated Tremor/Ataxia Syndrome-An Older Face of the Fragile X Gene.” 2007. In Nature Clinical Practice Neurology. Nature Publishing Group.
- ^ a b c Cite error: The named reference
seebergerwas invoked but never defined (see the help page). - ^ [3] Eidelberg, David, Pourfar, Michael. "Tremor." 2007. In The Merck Manuals Online Medical Library.
- ^ [4] Debiasi, R.L, Tyler, K.L. "West Nile Virus Meningoencephalitis: Diagnosis." 2006. In Nature Clinical Practice Neurology. Nature Publishing Group.
- ^ [5] “Epidemiological Notes and Reports Elemental Mercury Poisoning in a Household – Ohio 1989.” 1990. In Morbidity and Mortality Weekly Report. Centers for Disease Control and Prevention.
- ^ [6] “Medical Management Guidelines for Acute Chemical Exposures.” 1992. U.S Department of Human Health Services.
- ^ Wyne, Kevin. "A comprehensive review of tremor." 2005. In Journal of American Academy of Physician Assistants.
- ^ a b c [7] Purves, Dale et al. Neuroscience. Fourth Edition. 2008. Sinauer Associates, Inc.
- ^ Cite error: The named reference
reviewwas invoked but never defined (see the help page).