How Is ALS Confirmed? EMG, Nerve Studies and the Tests That Rule Out Similar Conditions

The first thing many people notice is oddly small. A thumb that will not grip a car key the way it used to. A word that comes out thick at the end of a long phone call. A calf that flickers under the skin at night, like a moth under a sheet. None of these things feel like a neurological emergency, and most of the time they are not one.

Yet for a small number of people, that small thing is the opening line of a much longer story, and the question that follows is the one this article is built around: how ALS is diagnosed when there is no blood test, no scan and no single number that can settle it. The honest answer is that neurologists confirm ALS the way a detective closes a case, by gathering evidence that fits one explanation and systematically ruling out every other suspect.

That process can feel slow and, at times, maddeningly indirect. Understanding why it works this way makes the waiting easier to bear and the questions easier to ask.

How ALS is diagnosed when no single test can confirm it

Amyotrophic lateral sclerosis, usually shortened to ALS and known in some countries as motor neurone disease, is a condition in which the nerve cells that control voluntary muscle gradually stop working and die. Those cells are called motor neurons. Because the damage happens inside the nervous system rather than in the blood, there is nothing to draw into a tube and measure, and the National Institute of Neurological Disorders and Stroke states plainly that no one test can provide a definitive diagnosis.

What exists instead is a set of converging clues. The first is the story a person tells: weakness that started in one place, spread to a neighboring area, and has never improved. The second is what the neurologist finds on examination, in particular evidence that two different sets of motor neurons are failing at once. The third is electrical testing that confirms muscles are losing their nerve supply even in places that still feel strong. The fourth, and in many ways the most reassuring, is a deliberate search for other diseases that can look identical from the outside but have very different treatments and outlooks.

Only when all four lines of evidence point the same way does a specialist feel able to say the word with confidence. That is why a diagnosis of ALS is rarely delivered at a first visit, and why a careful neurologist may seem, from the patient’s chair, to be doing a great deal of work to prove something other than ALS. That effort is the point. Every mimic that is excluded makes the eventual conclusion more solid, and occasionally the search turns up a condition that can be treated instead.

The sections that follow walk through each step in the order a person is likely to meet it.

What actually happens during an ALS workup, step by step

Most people arrive at a neurologist by way of a primary care clinician or an orthopedic or ear-nose-throat specialist who noticed something unusual. The neurology visit itself tends to follow a recognizable arc.

It begins with a long conversation. Expect questions about exactly when the weakness or speech change started, whether it has spread, whether there is pain or numbness, how work and hobbies have been affected, and whether any relative has had ALS or dementia. The absence of numbness matters as much as the presence of weakness, for reasons explained in the nerve conduction section below.

Next comes the physical examination, which often lasts longer than the conversation. The neurologist will watch you walk, ask you to speak and swallow, look at your tongue at rest, test the strength of individual muscle groups against resistance, tap tendons with a reflex hammer, and study your limbs for visible shrinkage or flickering. This examination is where the first crucial distinction is made between two kinds of motor neuron damage.

Electrical testing usually follows at a separate appointment. Electromyography, or EMG, uses a fine needle to listen to the electrical activity of muscles; nerve conduction studies use small skin shocks to measure how fast and how strongly signals travel along nerves. Imaging of the brain and spinal cord, blood tests and occasionally a spinal fluid sample round out the search for alternatives.

Then, in many cases, there is a pause. If the picture is suggestive but incomplete, the specialist may ask you to return in a few months for a repeat examination and EMG, because progression itself is one of the diagnostic criteria. The Mayo Clinic and the NHS both describe this staged, exclusion-based approach as standard practice rather than indecision.

Upper vs lower motor neuron signs: the exam findings that matter most

Two chains of nerve cells carry every deliberate movement. Upper motor neurons begin in the brain and run down the spinal cord; lower motor neurons begin in the spinal cord or brainstem and run out to the muscles. ALS is unusual because it damages both chains at once, and that dual pattern is the single most important thing a neurologist looks for on examination.

When lower motor neurons fail, muscles lose their direct supply. They waste away, becoming visibly thinner over weeks. They twitch involuntarily, producing the flickers under the skin that doctors call fasciculations. Reflexes in those muscles become weak or disappear, and the muscle tone feels floppy.

When upper motor neurons fail, the opposite happens to reflexes. Without the brain’s usual dampening signal, tendon reflexes become brisk and exaggerated, muscles feel stiff or tight, and the examiner may find abnormal reflexes such as the Babinski sign, in which the big toe fans upward when the sole is stroked. Speech may sound strained rather than slurred, and emotional expression can become harder to control.

Seeing both patterns in the same body region, such as a wasted, twitching hand paired with an exaggerated arm reflex, is highly suggestive. Cleveland Clinic and NINDS both describe this combination as central to recognizing ALS clinically. Many conditions can produce one pattern or the other; relatively few produce both together in a progressive, spreading way.

Neurologists organize the body into four regions for this purpose: bulbar (face, tongue, throat), cervical (arms and shoulders), thoracic (trunk and breathing muscles) and lumbosacral (legs). Diagnostic criteria, discussed later, count how many regions show each type of sign. A person may therefore find the examiner spending a surprising amount of time on limbs that feel perfectly normal.

EMG for ALS: what the needle test actually shows

Electromyography is the closest thing ALS has to a confirmatory test, though it never stands alone. A very thin needle electrode is placed into a muscle, and the electrical activity of that muscle is displayed on a screen and played through a speaker. Most people describe the sensation as a brief pinch followed by a dull ache; MedlinePlus notes the whole session commonly takes between 30 and 60 minutes depending on how many muscles are sampled.

A healthy muscle is electrically silent at rest. A muscle that has lost part of its nerve supply is not. Individual muscle fibers, cut off from their motor neuron, begin firing spontaneously, producing tiny signals called fibrillation potentials and positive sharp waves. Larger spontaneous discharges correspond to the visible twitches, and the electromyographer will often ask you to relax completely so these can be recorded.

When you are then asked to contract the muscle gently, a second clue appears. Surviving motor neurons try to compensate by sprouting new connections to orphaned fibers, so each remaining nerve cell controls an unusually large territory of muscle. On screen this shows up as motor unit potentials that are taller, wider and more jagged than normal, firing quickly because there are too few of them to share the work.

The combination of active nerve loss and chronic compensation, found in muscles across more than one body region and including muscles that feel strong, is what specialists mean when they say the EMG supports ALS. Crucially, the test can reveal lower motor neuron involvement in regions where the exam appeared normal, effectively expanding the number of affected regions.

An EMG cannot, on its own, distinguish ALS from every other cause of nerve-fiber loss. A compressed nerve root in the neck, for instance, can produce similar changes confined to one area. That is why the distribution of findings, and the results of the paired nerve conduction studies, matter as much as the findings themselves.

Nerve conduction studies: why normal sensory results are good evidence

Nerve conduction studies are almost always done in the same appointment as the EMG, usually first. Small sticky electrodes are placed on the skin, and a brief electrical pulse is delivered to a nerve. The machine measures how quickly the signal arrives at a recording point and how large the response is. The pulses feel like a static shock or a rubber-band snap; they are uncomfortable but not damaging.

Two properties are measured. Conduction velocity tells the examiner whether the insulating sheath around the nerve, called myelin, is healthy. Amplitude, the height of the response, tells them roughly how many nerve fibers are still working.

In ALS the results follow a characteristic pattern. Sensory nerves, the ones carrying touch and position information back to the brain, are typically normal, because ALS spares them. Motor nerve velocities are also usually normal or only mildly slowed, because the myelin is intact. What may fall is motor amplitude, reflecting the loss of motor neurons and the fibers they supplied.

This is why a person with suspected ALS may hear a neurologist sound quietly reassured by a normal sensory study. Many conditions that cause weakness, including most peripheral neuropathies and some spinal cord problems, also damage sensation. Normal sensory conduction narrows the field.

One finding in particular changes everything. If the examiner sees conduction block, a spot where the motor signal drops sharply between two points along a nerve, the leading suspect shifts to multifocal motor neuropathy, an immune-mediated condition that can produce weakness and wasting very much like ALS but that responds to immune-based treatment. NINDS lists it among the disorders that must be distinguished from ALS, and nerve conduction studies are the main way that distinction is made.

Taken together, EMG and nerve conduction studies answer two linked questions: are muscles losing their nerve supply in a widespread way, and is the damage confined to motor neurons? Both answers must be yes for ALS to remain the leading explanation.

MRI and imaging: ruling out look-alikes in the neck, brain and spine

Magnetic resonance imaging, or MRI, uses a strong magnetic field and radio waves to produce detailed pictures of soft tissue. In an ALS workup its role is almost entirely negative, in the best sense: it is ordered to find something else, and a clean scan is a piece of evidence in favor of ALS rather than against it.

The most common imaging target is the cervical spine, the portion of the spinal cord inside the neck. Arthritic narrowing of the spinal canal, herniated discs and bony spurs can squeeze the cord and the nerve roots leaving it, producing a combination of stiff, brisk-reflexed legs and wasted, weak hands that mimics ALS closely. Mayo Clinic notes that this condition, cervical spondylotic myelopathy, can be treated surgically in some people, which is precisely why it must be found or excluded early.

Brain MRI serves a different purpose. It can reveal multiple sclerosis, tumors, strokes in the brainstem, or structural problems at the junction of the skull and spine, any of which can affect speech, swallowing or limb strength. It may also show subtle changes along the motor pathways in ALS itself, but these are inconsistent and are not used to make the diagnosis.

Depending on where symptoms began, the thoracic or lumbar spine may be imaged as well, particularly when leg weakness is the presenting problem.

Newer imaging techniques that map the motor pathways in more detail remain research tools. The evidence that they can reliably confirm or exclude ALS in an individual is not yet strong enough for routine use, and NINDS describes imaging as a means of excluding other conditions rather than confirming ALS.

People are sometimes puzzled to be sent for an MRI of the neck when their trouble is in a hand. The neck is where the nerves to that hand leave the spinal cord. Checking it is one of the most useful things a neurologist can do before settling on a diagnosis that has no reversible cause.

Blood and spinal fluid tests: the conditions that mimic ALS

There is no blood test that detects ALS. There are, however, a number of blood tests that detect conditions capable of imitating it, and a thorough workup includes most of them. The NHS and NINDS both describe blood testing as a standard part of excluding alternatives.

A typical panel checks thyroid function, because an overactive thyroid can cause weakness, twitching and weight loss. It measures vitamin B12, since deficiency damages the spinal cord and can produce stiff legs and brisk reflexes. Calcium and parathyroid hormone are checked because hyperparathyroidism has been reported to cause a syndrome resembling ALS. Creatine kinase, a muscle enzyme, is often mildly raised in ALS as muscles waste, but a very high level points instead toward a primary muscle disease such as inclusion body myositis.

Protein electrophoresis looks for an abnormal antibody produced by a plasma cell disorder, which can be associated with motor nerve damage. Antibodies against a nerve component called GM1 ganglioside support the diagnosis of multifocal motor neuropathy. Tests for HIV, Lyme disease and syphilis are included where exposure is possible, since each has been associated with motor neuron syndromes. Where the history suggests it, heavy metal levels may be checked as well.

A lumbar puncture, in which a small sample of the fluid surrounding the spinal cord is drawn from the lower back with a thin needle, is not routine but is used when inflammation, infection or a cancer-related process is suspected. Muscle biopsy, once common, is now reserved for cases in which a muscle disease remains a realistic alternative after EMG.

One newer marker deserves mention. Neurofilament light chain is a protein released when nerve fibers are damaged, and levels in blood and spinal fluid are often elevated in ALS. Current evidence supports it as an aid to the overall picture and to research, not as a standalone diagnostic test, and it is not required by any accepted diagnostic criteria.

Genetic testing for ALS: who is offered it and what it can and cannot say

Most ALS is sporadic, meaning it appears in a person with no affected relatives. NINDS estimates that roughly 5 to 10 percent of cases are familial, passed down through a family, and that in those families a specific gene change can often be identified. The most frequently implicated genes are C9orf72, SOD1, TARDBP and FUS, each of which affects how motor neurons process proteins or RNA.

Genetic testing, which uses a blood or saliva sample to read specific genes, therefore plays two roles. In someone with a family history of ALS or of frontotemporal dementia, a related condition that shares some of the same genes, finding a known variant adds substantial weight to the clinical diagnosis. Increasingly, testing is also offered to people with apparently sporadic ALS, because a proportion of them carry the same variants without knowing it, and because some emerging treatments are designed for specific genetic forms.

What genetic testing cannot do is confirm or exclude ALS on its own. A negative result does not rule out the disease, since most people with ALS have no identifiable variant. A positive result in a healthy relative indicates elevated risk, not certainty, because some variants do not always cause disease and the age of onset varies widely.

For that reason, testing is usually preceded by a conversation with a genetic counselor, a professional trained to explain inheritance patterns and help people decide whether the information is wanted. Results can affect siblings and children as well as the person tested, and some people reasonably choose not to know.

Where a variant is found, the treating neurologist may discuss whether it opens the door to a particular therapy or clinical trial. That decision, like every other in the ALS pathway, sits with the specialist team and the person in front of them, weighing the evidence available at the time.

ALS vs conditions that mimic ALS: how the tests tell them apart

The table below summarizes the look-alike conditions most often considered in an ALS workup and the test result that typically separates each from ALS. It is a map of the neurologist’s reasoning, not a self-diagnosis tool; several of these conditions can only be distinguished by a specialist reviewing the whole picture.

Condition	Why it can resemble ALS	Key distinguishing finding
Cervical spondylotic myelopathy	Stiff legs, brisk reflexes and wasted hands from cord and root compression	MRI of the neck shows spinal cord compression; sensory changes often present
Multifocal motor neuropathy	Progressive, painless weakness and wasting, mostly in the arms	Conduction block on nerve conduction studies; anti-GM1 antibodies may be present
Kennedy disease (spinal and bulbar muscular atrophy)	Slow lower motor neuron weakness affecting face, tongue and limbs	Genetic test for the androgen receptor gene; sensory nerve abnormalities; no upper motor neuron signs
Inclusion body myositis	Weakness of finger flexors and thighs with swallowing difficulty	Markedly raised creatine kinase; muscle-pattern EMG; muscle biopsy
Myasthenia gravis	Slurred speech, swallowing trouble, limb weakness	Weakness fluctuates and worsens with fatigue; specific antibodies; repetitive nerve stimulation
Benign fasciculation syndrome	Persistent visible twitching	Normal strength, normal reflexes, no wasting, EMG without nerve loss
Hyperthyroidism or B12 deficiency	Weakness, twitching or spinal cord dysfunction	Abnormal blood levels; improvement with treatment of the deficiency

Two features stand out across the table. Sensory involvement, whether numbness on examination or abnormal sensory conduction, points away from ALS. So does any test result that identifies a reversible or treatable cause. NINDS and Cleveland Clinic both emphasize that the exclusion of these conditions is not a formality but a core part of how ALS is diagnosed.

Related motor neuron disorders sit close to ALS rather than opposite it. Primary lateral sclerosis affects only upper motor neurons, and progressive muscular atrophy affects only lower motor neurons. Both are typically slower, and both are sometimes reclassified as ALS if the missing pattern appears over time.

ALS diagnosis criteria: how neurologists put the evidence together

Once the tests are in, a neurologist compares the findings against published diagnostic criteria. These are structured checklists developed by international expert groups so that specialists in different places reach the same conclusion from the same evidence. Several versions exist, and you may hear their names: the El Escorial criteria, the Awaji criteria and the more recent Gold Coast criteria.

The older frameworks graded certainty. A person might be told the diagnosis was possible, probable or definite depending on how many of the four body regions showed upper and lower motor neuron signs. Those labels had a research purpose, but they caused understandable distress; being told one had probable ALS felt like being left in limbo, even though the underlying reality was usually the same.

The Gold Coast criteria simplified the approach into three requirements. First, there must be progressive motor impairment documented by history or repeated examination, following a period of normal function. Second, the examination or EMG must show upper and lower motor neuron dysfunction together in at least one body region, or lower motor neuron dysfunction alone in at least two regions. Third, investigations must have excluded other disease processes that could explain the findings.

Notice how each requirement maps onto the tests already described. Progression comes from the history and from the repeat visit. The motor neuron pattern comes from the examination and the EMG, with the EMG counting as evidence of lower motor neuron involvement in a region even when the muscles there feel strong. Exclusion comes from imaging, blood work and nerve conduction studies.

Criteria are tools for the specialist, not a score patients are expected to calculate. Their value lies in ensuring that the word ALS is used only when the evidence genuinely supports it, and that other explanations have been looked for rather than assumed away. A second opinion from another neurologist experienced in motor neuron disease is common and is generally welcomed by treating teams.

Who is fast-tracked to testing, and who is usually asked to wait and re-check

Not everyone with a twitch or a weak hand needs an urgent neurology workup, and part of the skill in this area is deciding who does. The pattern of symptoms drives that decision far more than the symptoms themselves.

A person is typically referred promptly when weakness is progressive, painless and asymmetric, meaning it started on one side or in one limb and has spread; when it is accompanied by visible muscle wasting; when speech has become slurred or swallowing effortful without another explanation; or when an examination shows both the floppy, twitching pattern of lower motor neuron loss and the stiff, brisk-reflexed pattern of upper motor neuron loss. Unexplained breathlessness lying flat, or a first-degree relative with ALS, also moves things along.

By contrast, twitching alone, without weakness, wasting or reflex change, is very common and rarely leads to ALS. Cleveland Clinic and other mainstream sources describe benign fasciculation as widespread in healthy adults, often worsened by stress, caffeine, poor sleep or exercise. Someone with isolated twitching and a normal examination is usually reassured and may be asked to return only if strength changes. A normal EMG in that setting is strongly reassuring.

Between these groups lies a middle ground: a person with genuine but limited findings, such as wasting in one hand with an otherwise normal examination. Here the neurologist may deliberately wait. Progression is itself a diagnostic requirement, so a repeat examination and EMG after a few months can turn an ambiguous picture into a clear one, in either direction. Mayo Clinic notes that this observation period is a recognized part of reaching an accurate diagnosis.

Waiting is hard. It helps to know that it is being done to avoid two errors that are each serious: labeling someone with ALS who does not have it, and missing a treatable alternative because the label was applied too soon.

How long does it take to diagnose ALS, and what the following weeks look like

People consistently ask how long the process takes, and the honest answer is that it is measured in months rather than weeks. The reasons are built into the disease. Early symptoms are easily attributed to more common problems, several specialists may be seen before a neurologist, and once a neurologist is involved the diagnostic criteria require documented progression, which by definition takes time. NINDS describes the diagnosis as based on a detailed history, examination and a series of tests over time, and both Mayo Clinic and the NHS note that repeat assessment is often needed.

In the weeks after the first neurology visit, expect the electrical tests and imaging to be scheduled, usually as outpatient appointments. Blood results typically return within days. If the picture is incomplete, a follow-up visit is arranged, commonly a few months out, for a second examination and often a second EMG.

If the findings meet criteria, the diagnosis is usually delivered face to face by the neurologist, often with a nurse specialist present, and ideally with a family member or friend alongside. Most people describe the conversation as a blur; asking for a written summary and a named contact for questions is reasonable and common.

What follows is referral into a multidisciplinary team. The NHS and NINDS describe this as the standard model of care: a neurologist, specialist nurse, physiotherapist, occupational therapist, speech and language therapist, dietitian, respiratory specialist and often a social worker or counselor, working together rather than in sequence. Early meetings focus on baseline measurements, including breathing tests, swallowing assessment and strength, so that changes can be tracked and support introduced before it becomes urgent.

Many people find that this period, painful as it is, also brings a strange relief. A name has been put to something that was frightening precisely because it was unnamed, and a team now exists whose job is to walk alongside them.

Can ALS be stopped if caught early? What treatment after diagnosis involves

This is among the most searched questions about ALS, and it deserves a straight answer. At present, no available treatment stops or reverses ALS, and an earlier diagnosis does not change that fact. What earlier diagnosis does is open the door sooner to treatments intended to slow progression and to supportive care that protects breathing, nutrition, communication and independence. NINDS is explicit that current treatments cannot reverse the damage but can help control symptoms and slow decline.

Two classes of disease-modifying medicine are approved in the United States for ALS in general. One, riluzole, is thought to reduce the release of glutamate, a chemical messenger that in excess can damage motor neurons. Another, edaravone, is described as a free-radical scavenger that limits oxidative stress inside nerve cells. A third, tofersen, is designed for people with a specific SOD1 gene variant and works by reducing production of the abnormal protein. Whether any of these is appropriate, and when to start, is a decision for the treating neurologist, who weighs the individual’s findings, other health conditions and preferences.

Much of what changes daily life comes from the wider team rather than a prescription. Non-invasive ventilation, a mask device that supports breathing during sleep, is introduced when respiratory tests indicate it will help. Speech therapists assess swallowing and can teach strategies that reduce choking risk, and dietitians address the weight loss that commonly accompanies ALS. Physiotherapists and occupational therapists help maintain function and adapt homes and workplaces. Communication devices, including eye-tracking systems, are introduced ahead of need so that people can learn them while speech is still usable.

Clinical trials are an active area, and many specialist centers will discuss eligibility. Enrolment is entirely voluntary and never a condition of receiving standard care. The right time to raise any of these options is whenever a person wants to, and the team should be the ones to help sort through them.

What people often get wrong about ALS and how it is diagnosed

Misunderstandings about ALS cause real harm, in both directions. Some people spend months convinced they have it when they do not; others dismiss early signs because they do not match the picture they carry in their heads. A few corrections are worth making.

Twitching is not a diagnosis. Fasciculations occur in most healthy adults at some point and, on their own, almost never indicate ALS. In ALS, twitching accompanies weakness and wasting rather than preceding them by months in a person who is otherwise strong. An internet search for muscle twitching returns ALS near the top for reasons of fear rather than probability.

There is no blood test, scan or single procedure that confirms ALS. Anyone told otherwise, or offered a paid test promising certainty, should be skeptical; mainstream sources including NINDS and Mayo Clinic are unanimous that diagnosis rests on the full clinical picture.

ALS is not only a disease of older men. NINDS notes that most people develop symptoms between ages 55 and 75, but it can begin much earlier, and while men are affected somewhat more often than women, the difference narrows with age. Nor does it affect only the limbs; roughly a quarter to a third of people first notice changes in speech or swallowing, according to NINDS and Cleveland Clinic descriptions of bulbar-onset disease.

Nothing a person did triggered it. The question of what starts ALS is a genuine scientific unknown. Genetic variants account for a minority of cases; for the rest, research points toward a combination of genetic susceptibility and environmental factors that has not been pinned down, with military service and some occupational exposures under study. No diet, injury, vaccine or lifestyle choice has been shown to cause ALS, and blaming oneself has no evidentiary basis.

Finally, numbness and pain are not typical early features. Their presence should prompt a search for something else, not be squeezed into an ALS narrative.

Questions to ask your care team during an ALS workup

Appointments in this pathway are dense, and questions evaporate under stress. Writing them down beforehand, and bringing someone to take notes, changes the experience. The following are questions people who have been through the process often wish they had asked earlier.

• Which other conditions are you considering, and which tests are designed to rule each of them out?
• What did my EMG and nerve conduction studies show, in plain terms, and in how many body regions?
• Were there any findings that do not fit ALS, and how are you interpreting them?
• Do I meet formal diagnostic criteria now, or is this a working diagnosis that you expect to confirm with time?
• If we are waiting for a repeat examination, what specifically will you be looking for, and what should prompt me to come back sooner?
• Is genetic testing relevant for me, and can I speak with a genetic counselor before deciding?
• Would a second opinion be reasonable, and can you help arrange one?
• When will I be introduced to the multidisciplinary team, and who is my main point of contact between visits?
• What breathing and swallowing assessments will be done as a baseline, and how often will they be repeated?
• Are there clinical trials I might be eligible for, and what would taking part involve?
• What symptoms should I report immediately rather than wait for the next appointment?
• Who can my family talk to about what this means for them?

There is no such thing as a question a good team resents. Neurologists who work in this field expect the same questions to return at successive visits as the picture changes and as people absorb information in stages. Asking again is not a failure to listen; it is how understanding actually forms under pressure.

If English is not your first language, or if hearing or processing information is difficult, ask for an interpreter or for written material in advance. Both are standard requests.

When to call your doctor

Two situations call for a phone call rather than a wait. The first is when symptoms that might point toward a motor neuron problem are new, progressive and unexplained. The second is when a person already under investigation or living with ALS develops a change that could affect breathing or swallowing.

Seek an appointment promptly if you notice weakness in a hand, arm, foot or leg that has persisted for more than a few weeks and is getting worse rather than better; visible thinning of a muscle, often first seen in the hand or shoulder; muscle twitching that is accompanied by weakness or shrinkage rather than occurring on its own; slurred or effortful speech, or difficulty swallowing, that has no obvious cause such as a sore throat; frequent tripping, foot dragging or a new inability to stand on tiptoe; or unusual difficulty breathing when lying flat. Any of these warrants evaluation, and most will turn out to have another explanation, which is exactly why they should be assessed rather than searched online.

Call urgently, or use emergency services, if there is choking or food going down the wrong way repeatedly, sudden or rapidly worsening shortness of breath, difficulty breathing that disturbs sleep or causes morning headaches and confusion, a fall with a head injury, or an inability to clear the chest during a respiratory infection. For people with known ALS, the NHS and NINDS both highlight that breathing problems and chest infections can escalate quickly and that early contact with the specialist team is appropriate.

None of the tests described in this article should be self-ordered, and none of the medicines mentioned should be started, stopped or changed without the prescribing clinician. Every decision about investigation and treatment belongs with the treating team, who can see the whole picture that no article can.

Frequently asked questions

How do doctors confirm ALS?

Doctors confirm ALS by assembling a consistent pattern rather than by one test. A neurologist documents progressive weakness with no sensory loss, finds both upper motor neuron signs such as brisk reflexes and lower motor neuron signs such as wasting and twitching, uses EMG to show nerve loss in multiple body regions, and orders MRI, blood tests and nerve conduction studies to exclude conditions that mimic ALS. Formal criteria are then applied.

What are the first signs of ALS?

The first signs of ALS are usually painless weakness or clumsiness in one hand, arm, foot or leg, sometimes with visible muscle thinning and twitching, or slurred speech and swallowing difficulty when the disease begins in the bulbar region. Symptoms start in one area and spread. Numbness, pain and twitching without weakness are not typical early features and usually point to something else.

Can ALS be stopped if caught early?

No currently available treatment stops or reverses ALS, and earlier diagnosis does not change that. What early diagnosis offers is sooner access to medicines intended to slow progression, to breathing and swallowing support introduced before it becomes urgent, and to clinical trials. Decisions about any of these rest with the treating neurologist and multidisciplinary team, based on the individual’s findings and preferences.

What triggers ALS to start?

The trigger for ALS is not known. Roughly 5 to 10 percent of cases are familial and linked to identified gene variants such as C9orf72 or SOD1. For the remainder, research points toward a mix of genetic susceptibility and environmental factors that has not been pinned down. No diet, injury, infection, vaccine or lifestyle choice has been shown to cause ALS.

What does an EMG for ALS show?

An EMG for ALS typically shows two things together. At rest, muscles that have lost nerve supply fire spontaneously, producing fibrillation potentials, positive sharp waves and fasciculation potentials. During gentle contraction, surviving motor neurons appear as unusually large, jagged signals firing rapidly because too few remain. Finding this combination in several body regions, including muscles that feel strong, supports the diagnosis when other causes are excluded.

Can an MRI or blood test diagnose ALS?

No. MRI and blood tests cannot diagnose ALS; they are ordered to find other explanations for the symptoms. MRI of the neck can reveal spinal cord compression, and brain MRI can show multiple sclerosis or tumors. Blood tests check thyroid function, vitamin B12, calcium, muscle enzymes, abnormal antibodies and infections. Normal results make ALS more likely by narrowing the alternatives, but they do not confirm it.

What are the ALS diagnosis criteria neurologists use?

Neurologists most often use the Gold Coast criteria, which require three things: progressive motor impairment following a period of normal function; upper and lower motor neuron dysfunction in at least one body region, or lower motor neuron dysfunction in at least two; and exclusion of other diseases by appropriate investigations. Older El Escorial and Awaji criteria graded certainty as possible, probable or definite and are still used in research.

Which conditions mimic ALS most often?

The conditions that most often mimic ALS include cervical spondylotic myelopathy from spinal cord compression, multifocal motor neuropathy, Kennedy disease, inclusion body myositis, myasthenia gravis, and deficiencies or hormone problems such as low vitamin B12 or overactive thyroid. Benign fasciculation syndrome mimics only the twitching. Each is separated from ALS by specific findings on imaging, nerve conduction studies, blood work or genetic testing.

Does muscle twitching mean I have ALS?

Muscle twitching on its own almost never means ALS. Fasciculations are common in healthy adults and are often worsened by stress, caffeine, exercise or poor sleep. In ALS, twitching accompanies weakness and visible muscle wasting rather than appearing alone. If twitching is combined with weakness, shrinkage or changed reflexes, a neurological examination is appropriate; a normal examination and EMG are strongly reassuring.

Should I get a second opinion after an ALS diagnosis?

Seeking a second opinion after an ALS diagnosis is common and generally encouraged by treating teams, because the diagnosis carries major consequences and rests on clinical judgment rather than a single test. A neurologist experienced in motor neuron disease can review the examination, EMG and exclusion tests. Ask your current team to help arrange it; doing so does not delay referral to a multidisciplinary clinic.

References

• Amyotrophic Lateral Sclerosis (ALS): National Institute of Neurological Disorders and Stroke
• Motor neurone disease: NHS
• Amyotrophic Lateral Sclerosis (ALS): Cleveland Clinic
• Electromyography (EMG) and Nerve Conduction Studies: MedlinePlus

This article is for general information only and is not a substitute for professional medical advice. Please consult a qualified doctor about your individual situation.