Amyotrophic lateral sclerosis is difficult to be diagnosed since the beginning, because it may seem similar to some other neurological diseases. The medical experts caution after conducting a neurological examination tests to rule out other conditions, with signs of UMN and LMN in the same segment with asymmetrical anatomical localization is able to suspect the diagnosis of ALS. Examination that may be performed include:
1 . Electrophysiology
Primarily to detect the presence of LMN lesions on the area involved . And to rule out other disease processes . It's important to remember that only a physical examination neurophysiology that is used to diagnose ALS and neurophysiological abnormalities suggestive , is not enough to diagnose without clinical support .
a. Motor and sensory nerve conduction
Nerve conduction required to diagnose especially to define and exclude other disorders of peripheral nerves, neuromuscular junction, and muscle disorders that may mimic or confound the diagnosis of ALS .
b . conventional electromyography
Concentric needle electromyography (EMG) provide evidence of LMN dysfunction are needed to support the diagnosis of ALS, and to be found in at least two of the four regions CNS : brain (bulbar / cranial motor neurons), cervical, thoracic, or lumbosacral spinal cord (anterior horn motor neurons). For the area of the brain stem that is enough to show changes in the muscle EMG (eg, tongue , facial muscles, jaw muscles). For the region of the spinal cord, chest it is enough to show EMG changes both in the paraspinal muscles at or below T6 level or in the abdominal muscles. For the cervical region and bone marrow lumbosacral back at least two muscles innervated by different roots and peripheral nerves must show EMG changes
El - Escorial criteria revised requires that both the evidence
active or ongoing denervation and chronic partial denervation is required for the diagnosis of ALS, although the relative proportion varies from muscle to muscle .
Signs of active denervation consist of :
1 . fibrillation potentials
2 . positive sharp waves
Signs of chronic denervation consist of :
1. Motor unti great potential duration increased with an increased proportion of polyphasic potentials, amplitude often increased .
2. reduce the interference pattern with a higher firing rate of 10 Hz (unless there is a significant component of UMN, in terms of the rate of combustion may be lower than 10 Hz ) .
3. stable motor unit potentials .
Fasciculation potential is very important to find the characteristics of ALS, although they can be seen in normal muscle (benign fasciculations) and does not appear in all the muscles of ALS patients. In benign fasciculation morphology of normal fasciculation potentials, whereas the fasciculation potential changes associated with neurogenic no abnormal morphology and positive sharp complex c. Transcranial magnetic stimulation and central motor conduction Transcranial magnetic stimulation (TMS) allows non- invasive evaluation of the corticospinal motor pathways, and allows detection of UMN lesions in patients who have no signs of UMN. Motor amplitude, cortical threshold, time
central motor conduction and silent periods can be easily evaluated by using this method. Central motor conduction time ( CMCT ) is often a little longer for the muscles at least one limb in ALS patients.
d . quantitative electromyography
Motor unit number estimation ( mune ) is a specific electrophysiological technique that can provide quantitative estimates of the number of axons that innervate muscle or muscle group . Mune is composed of a number of different methods
( incremental , multiple point stimulation , spike - triggered average , F - wave , and statistical methods ) , with each having specific advantages and
limitations . Despite the lack of a single perfect method to make Mune , may have value in the assessment of progressive loss of motor axons in ALS , and may have use as a
endpoint measure in clinical trials
2 . Neuroimaging
MRI head / spine to rule out structural lesions and other diagnoses in patients suspected ALS (tumors, spondylitis, Syringomyelia , bilateral stroke, and MS)
3 . Muscle biopsy and neuropathology
mainly conducted in patients with atypical clinical presentation , escpecially with UMN lesions is not clear. Biopsy is used to rule out the presence of myopathy, such as inclusion body myositis.
4 . Other laboratory tests
There are several other tests that may be considered mandatory in the examination of ALS patients . Clinical laboratory tests may be abnormal in cases of otherwise typical ALS include :
• muscle enzyme ( creatine kinase serum [ unusual above ten times the upper limit of normal ] , ALT , AST, LDH )
• serum creatinine ( associated with loss of skeletal muscle mass)
• Hypochloremia , bicarbonate increases ( associated with respiratory disorders chronic )