Functional MRI in Determining Language Lateralization

Abstract

OBJECTIVE: Amiotrophic Lateral Sclerosis (ALS) is a disorder

characterized by upper and lower motor neuron degeneration.

Electrophysiologic studies such as electromyography are helpful for do-

cumenting lower motor neuron dysfunction while, a method to routine-

ly evaluate upper motor neuron (UMN) dysfunction is not available.

Recently transcranial magnetic stimulation (TMS) has become a populer

method for the evaluation of central motor pathways. This method is

especially useful in patients with no clinical UMN dysfunction.

The aim of this study was to evaluate the role of TMS in

demonstrating UMN dysfunction in ALS patients.

METHODS: A motor evoked potential study with TMS was

performed on 13 ALS patients and 10 healthy controls. Cortical motor

threshold (CMT), cortical silent period, motor evoked potential latency

and amplitude and central motor conduction time were the parameters

evaluated.

RESULTS: The most sensitive parameter was found to be CMT, while

none of the other parameters were found to be statistically significant

between the patients and controls.

CONCLUSION: It is known that in ALS patients different CMT changes

may occur depending on the disease stage. In the early period with glutamate induced hyperexitability the CMT decreases, while in the late

stage of the disease the CMT increases due to cortico-motor neuron

loss. Cortical exitability changes are specific for ALS. TMS is a painless,

easy and sensitive method which at the present time helps the diagno-

sis of ALS but hopefully in the future may also hold a light to the patho-

genesis and treatment of ALS.