TMS and the Neurology of Alzheimer's
Basic findings
One of the earliest TMS and Alzheimer’s Disease (AD) studies by Perretti et al. (1996) suggested that loss and/or dysfunction of motor cortex neurones, including pyramidal cells and inhibitory interneurones may occur in AD patients before clinical signs become apparent. The motor threshold in AD patients has been shown to be lower than in normal subjects with a significant correlation between the stage of cognitive severity (Alagona et al., 2001)
Ongoing research
Monitoring The Disease
The amount of short latency afferent inhibition (SAI) is significantly smaller in early AD patients than in controls. Identification of SAI abnormalities that occur early in the course of AD will allow earlier diagnosis (Nardone 2008).
Previous TMS studies have demonstrated hyperexcitability and asymptomatic motor cortex reorganization in the early stages of AD in patients with normal motor function, Ferreri et al. (2011) compared motor cortex functionality in AD patients before and after long-term Acetylcholinesterase Inhibitor therapy in order to monitor potential drug-related changes in cortical excitability and organisation. These authors summarised that TMS, along with clinical, neuropsychological, and neuroimaging data, could be an inexpensive measure of biological progression in AD and it might supplement traditional methods to assess the effects of therapy (Ferreri et al., 2011).
Based on different patterns of cortical excitability, TMS may also be useful in discriminating between physiological brain aging, mild cognitive impairment, AD and other dementing disorders (Pennisi et al 2011).
Modulating The Disease
TMS can induce acute and short-duration beneficial effects on cognitive function (Freitas et al., 2011). Cotelli et al. (2008) noted that their findings suggest that rTMS can affect the intrinsic ability of the brain to restore or compensate for damaged function and may represent a useful new tool for cognitive rehabilitation. In a more recent study, Cotelli et al. (2011) assessed the long-term effects on cognitive performance of rTMS applied to the left dorsolateral prefrontal cortex in AD patients. Their results showed an improvement in performance with respect to baseline or placebo and a lasting effect on the improved performance eight weeks after the end of treatment. Their findings provide initial evidence for the persistent beneficial effects of rTMS on sentence comprehension in AD patients.
Links
References
- Alagona et al., Neuroscience Letters, 2001.
- Cotelli et al., Arch Neurol, 2006.
- Cotelli et al., Eur J Neurol, 2008.
- Cotelli et al., J Neurol Neurosurg Psychiatry 2011.
- Di Lazzaro et al., J Neurol Neurosurg Psychiatry, 2005.
- Ferreri et al., Neuroscience Letters, 2011.
- Ferreri et al., Experimental Gerontology, 2011.
- Nardone et al., Journal of Neural Transmission, 2008.
- Pennisi et al., Journal of Neural Transmission, 2011.
- Perretti et al., J Neurol Sci, 1996.
