Amyotrophic lateral sclerosis (ALS) is better known in the United States and Canda as Lou Gehrig disease. It comes under the umbrella of a group of progressive neurological disorders collectively known as Motor Neuron Diseases (MNDs. ALS is a devastating neurological condition and is uniformally fatal in its outcome.
As the name suggests ALS involves the motor neurons selectively. What are motor neurons you may ask? Motor neurons are neurons (nerve cells) that control voluntary muscle activity. The motor neurons that control voluntary activity like swallowing, coughing, breathing and speaking lie in the brain stem while those that control voluntary activity like walking and moving your hands lie in the spinal cord.
ALS affects motor neurons of both the brain stem as well as the spinal cord. The disease by defination affects only the motor neurons and spares all sensory neurons. Thus patients with ALS have progressive motor weakness but no sensory findings ( no numbness or sensory loss). The disease also spares other brain functions like memory, cognition, orientation, alertness, ability to calculate, eye movements and bladder/bowel function.
That is why ALS is so devastating: it leaves one quadriplegic (completely paralyzed) having difficulty with swallowing, difficulty speaking and breathing but intact of all higher mental functions. Imagine been in a situation where your mind is completely healthy trapped in a completely paralyzed body.
ALS usually affects people in their late 40's and above. The disease has been known to occur in the younger age groups but in these rare cases it usually runs in the family an entitiy called familial ALS (FALS). The onset of the disease is very insidious and patients may present to their doctor with complaints of a wrist drop or foot drop ( inability to lift the wrist or the foot). Usually the bulbar symptoms of difficulty in swallowing and speaking come later on in the disease course. There is a constellation of signs and symptoms which physicians look for clinically when trying to secure a diagnosis of ALS.
Though this is technical let me try to explain it to you. If we as physicians find weakness in an arm or leg and the muscles are visibly atrophic (shrunken) but the reflexes (these are the reflexes which we elict by tapping your tendons with our hammers) are brisk, we think about possible ALS. If we find these signs in 3 different limbs it makes the diagnosis more secure. We also look for fasiculations. Fasiculations are visible involuntary muscle twitches under the skin arising from spontaneous discharge of motor neurons. In ALS one may see widespread fasciculations involving different muscle groups as well as fasciculations in the tongue (remember the tongue is also a muscle).
A word of caution here. A lot of us have visible fasciculations, we all have experienced the feeling when one of our muscle such as the eye-lid or thigh suddenly starts twitching. These are called benign fasciculations and do not protend ALS. Only when fasciculations are accompanied by visible muscle wasting and weakness that one should be worried. Benign fasciculations usually occur when one is tired or after heavy exercise and dehydration.
Other symptoms which commonly occur in patients with ALS include cramping especially of bigger muscle groups like that of the back.
If a diagnosis of ALS is been considered, it is imperative that other diseases which can mimic ALS in their presentation be ruled out. Some of these are readily treatable as against ALS for which currently we have no effective treatments. So how is the diagnosis of ALS secured?
When ALS is advanced, the diagnosis is readily apparent on a routine clinical neurological examination. The patient has visible atrophy (wasting) of the muscles of the limbs. Wide-spread fasiculations (muscle twitches) are visible to the naked eye. We as neurologists search for these in the tongue and the big muscle groups on the back. To secure the diagnosis in the earlier stages of the disease when the clinical features are not so florid, your doctor may order a few tests. The most important among these is the EMG (electromyogram). The EMG is a test which is not as bad as it looks. It basically involves putting a recording needle electrode in different muscles of the limbs, back and even the tongue to look for signs of denervation (damage to the motor nerves). There are criteria on EMG that help secure the diagnosis of ALS.
Management Issues in an ALS patient: ALS as a disease is incurable as of now. That said there is a lot which can be done to help a patient with ALS. Only one medication by the name of riluzole is approved for the treatment of ALS. That too prolongs the life expectancy by only a few months. Patients with ALS need a multitude of services and their care is best handled by a multi-speciality team consisting of neurologists, respiratory therapists, gastroenterologist, physical and occupational therapists and speech therapists. As the disease progresses and takes its toll, patients are prone to pneumonia and other respiratory tract infections. As their swallowing and speech functions become progressively impaired, nutrition (feeding) may have to be accomplished via either a feeding tube or a tube in the stomach (we call this a PEG tube). Physical and occupational therapy helps to preserve motor functions. These patients are greatly helped by assist devices like motorized wheel chairs, a simple straw to aid them in drinking water and other liquids etc.
Tremendous research is going on to find a cure for ALS. Your doctor might also prescribe some vitamins and supplements like coenzyme Q 10. Whether these help is doubtful but they most likely do not cause any harm. You should discuss and other experimental therapies with your physician.
Some diseases which may resemble ALS superficially in their presentation:
1) Benign Cramping Fasiculation Syndrome: I explained this above. A lot of people have visible fasiculations (their muscles quiver) and they may also have complaints of cramps. There is no associated muscle weakness or atrophy. Reassurance is all that is needed.
2) Multi-focal motor neuropathy with conduction blocks: an uncommon neurological condition characterized by involvement of multiple motor nerves (thus resulting in weakness). Conduction blocks are present in nerve conduction study. It resembles ALS in that it presents with weakness and does not cause sensory symptoms.
3) High cervico-medullary junction involvement--if there is a high cervical disk herniation, it at times can present just like ALS.
4) X-linked spinal and bulbar muscle atrophy also referred to as Kennedy's disease: neuromuscular disease due to mutations in the androgen receptor. Presents with cramps and progressive weakness due to degeneration of motor neurons in the brainstem and spinal cord.
It is imperative that the above conditions be looked for and ruled out before a diagnosis of ALS is arrived at, as some (multi-motor motor neuropathy with conduction blocks) do respond to therapies like intravenous immunoglobulin.
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