Neurological Disorders: ALS

What is this condition?

ALS (Amyotrophic lateral sclerosis), called as Lou Gehrig’s Diseases as well, is the commonest type of motor neuron disease in adults. Lou Gehrig was the famous US baseball player who succumbed to this disease so this disease is generally identified with his name, especially in the USA.

Motor neuron disorders (MND), as the name implies affect the motor neurons of the brain & spinal cord. Neurons are nerve cells and they are the functional units of the nervous system. Motor neurons control the motor activities, for example the muscle movements or muscle contraction etc.

In amyotrophic lateral sclerosis there is degeneration of motor neurons in the cerebral cortex, brain stem & spinal cord, and the fibers and tracts connected with these motor neurons like the corticospinal tract (sometimes called as pyramidal tract), motor fibers of the cranial nerves and peripheral nerves. This results in progressive weakness of skeletal muscles, which are called as voluntary muscles too since these muscles are under out voluntary control.

Who gets this disease?

It can affect a person from any race or ethnicity. Late middle age is the typical age at which this disease usually manifests (around 40 to 60 years). A small percentage of amyotrophic lateral sclerosis are generically based (hereditary based) and these hereditary cases start manifesting earlier than the sporadic cases (non-hereditary cases). Both genders are affected.

What causes it?

What exactly triggers motor neuron disease is still not fully known however it is generally considered that the free radical toxicity induced neuronal degeneration is a possibility.

A small percentage (about 5%) of this disease is familial and as pointed earlier above these cases present earlier compared to the sporadic cases (random cases or non-hereditary cases).

How does a patient present with this disease?

A patient with this disease characteristically shows a combination of both upper motor and lower motor neuron findings. Some upper motor neuron findings include brisk deep tendon reflexes, babinski sign, clonus etc. Some lower motor neuron findings include muscle wasting (thinning or atrophy), fasciculation or muscle twitching etc. Progressive muscle weakness, another important finding of this disease occurs due to both upper motor and lower motor neuron damage.

Clinical manifestations are usually asymmetric to start with eventually becomes bilateral and diffuse. Muscle twitchings (also called as fasciculations) are common. As disease progresses patients will have bulbar muscle weakness (tongue, throat etc) so will have difficulty with speech, swallowing, breathing etc. Breathing function is compromised too due to respiratory muscle paralysis and is an important cause for death in majority of the patients.

Bowel, bladder, eye muscle & cognitive involvement (dementia) are not typical features of this disease. If these manifestations are seen, especially early in the disease then one should suspect some other neurological disease rather than the Amyotrophic lateral sclerosis. However there is a rare variant of Amyotrophic lateral sclerosis with dementia as one of its early manifestation though, but this variant is not common.

Diagnosis

Once clinically a suspicion is made then patient will undergo an EMG/NCS (electromyography & nerve conduction study). The typical EMG findings include fasciculation, fibrillation potentials, and positive sharp waves along with few other abnormal changes. These changes should be seen on multiple regions; at least 3 out of 4 regions which include the lower limbs, thorax, upper limbs, and the head/face/bulbar muscles.

In straightforward cases clinical evaluation + EMG test may be sufficient but in borderline cases additional tests like MRI of the craniospinal junction and various blood tests are accomplished to rule out conditions that may mimic the motor neuron diseases.

Treatment

There is no cure for Amyotrophic lateral sclerosis as of now and the disease is invariably fatal in the next few to several years after the diagnosis is made.

Treatment is supportive & symptomatic. Riluzole is an FDA approved drug for this condition however it only provides a small delay in the requirement for ventilators for these patients. Physical therapy, patient & family counseling, hospice care are mainstays of the treatment.

Although a fatal disease now but lots of research activity is going on and there is a hope that a curative treatment may be available at some point in the future for this neurodegenerative condition.

A Neurologist is frequently involved in the care of ALS (Amyotrophic Lateral Sclerosis) patients.



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