ALS (amyotrophic lateral sclerosis) causes progressive muscle weakness that typically starts in one area of the body and spreads over time. Early symptoms are often subtle: a weakened grip, tripping while walking, slurred speech, or muscle twitching. Because these signs can mimic other conditions, diagnosis takes an average of 10 to 17 months from the first medical consultation, depending on whether you see a specialist or a general neurologist.
Around 33,000 people in the United States are living with ALS at any given time. The disease damages two types of nerve cells: those in the brain that initiate movement and those in the spinal cord that relay the signal to muscles. That dual damage is what makes ALS distinct and is why the symptom picture includes both muscle stiffness and muscle wasting.
Where Symptoms Usually Start
About three quarters of ALS cases begin in the limbs, most often in one hand, arm, foot, or leg. You might notice difficulty buttoning a shirt, turning a key, or opening jars. In the legs, the first sign is frequently tripping, a foot that drags, or trouble climbing stairs. These problems can feel lopsided at first, affecting one side more than the other.
The remaining cases begin with what doctors call “bulbar onset,” meaning the earliest symptoms involve the muscles of the face, jaw, throat, and tongue. Bulbar-onset ALS generally shows up as slurred speech, difficulty chewing or swallowing, excessive choking, or a voice that sounds hoarse, strained, or quieter than usual. Some people notice their tongue twitching or that they can’t articulate words they used to say easily.
Regardless of where symptoms appear first, fatigue, muscle cramping, and brief muscle twitches (fasciculations) are common early features. Muscles may feel either soft and weak or unusually stiff and tight. Many people also describe poor balance before any obvious weakness sets in.
Stiffness vs. Weakness: Two Kinds of Damage
ALS produces two distinct patterns of symptoms because it attacks two different sets of motor nerves. Damage to the nerves that run from the brain causes stiffness and tightness in muscles, a condition called spasticity. Your limbs may feel rigid, and reflexes can become exaggerated. Damage to the nerves running from the spinal cord to the muscles themselves causes weakness, visible muscle shrinkage (atrophy), and twitching.
Most people with ALS experience a mix of both patterns, though the balance varies from person to person. One person may deal primarily with stiffness and slow movement, while another loses strength rapidly with little stiffness. This variability is one reason ALS can be hard to recognize early on.
Speech and Swallowing Problems
Even in people whose ALS starts in a limb, speech and swallowing difficulties typically develop as the disease progresses. Early speech changes include poor articulation, a decrease in vocal range or loudness, and a harsh or strained voice quality. Words may come out slurred or take noticeable effort to form.
Swallowing problems create several practical challenges. Food may feel like it sticks in the throat, liquids may go down the wrong way, and meals take longer. Excess saliva can become an issue because weakened throat muscles make it harder to swallow at a normal rate. Weight loss from difficulty eating is a meaningful concern as these symptoms advance.
Breathing Changes
Respiratory symptoms tend to appear later in the disease course, though they can occasionally be the first sign. Research shows that instability in the upper airway typically emerges around 18 months into the illness. Early respiratory symptoms are easy to miss: shortness of breath when lying flat, disrupted sleep, morning headaches from poor overnight oxygen levels, and fatigue that seems out of proportion to activity.
The breathing muscles, including the diaphragm, gradually weaken, reducing the lungs’ capacity to move air. Nighttime breathing is affected first because the diaphragm does more work when you’re lying down. Many people eventually use a noninvasive ventilation mask, particularly during sleep, to support breathing before symptoms become severe.
Cognitive and Behavioral Changes
ALS was long considered a purely physical disease, but that understanding has changed significantly. Up to half of all people diagnosed with ALS experience some degree of cognitive or behavioral change. For most, these shifts are gradual and subtle: greater difficulty with planning, decision-making, or multitasking. You might notice a family member with ALS becoming more easily distracted or slower to work through problems they once handled quickly.
About 15% of people with ALS develop a more serious condition called frontotemporal dementia. Symptoms include behavior that seems out of character, impulsivity, apathy, poor social judgment, mental rigidity, irritability, and repetitive behaviors. Changes in language ability can also occur. These cognitive symptoms reflect damage to the frontal and temporal lobes of the brain, regions that overlap with the motor areas ALS affects.
What ALS Does Not Affect
One of the defining features of ALS is what it spares. The disease does not typically affect your senses. Taste, smell, touch, hearing, and vision remain intact. Bladder and bowel control are also generally preserved, which distinguishes ALS from many other neurological conditions. Eye movement is another function that stays normal well into the disease, which is why some people with advanced ALS communicate using eye-tracking technology.
Pain is not a direct symptom of the nerve damage in ALS, though many people do experience pain indirectly. Muscle cramps, joint stiffness from reduced movement, and the strain of compensating for weak muscles can all cause significant discomfort.
How Symptoms Progress
ALS symptoms almost always begin in one region and spread to others over months. A person whose weakness started in the right hand may notice the left hand weakening next, followed by the arms, then the legs. The pattern varies, but the general trajectory is expansion from one body area to adjacent areas.
Doctors track progression using a 12-domain functional scale that covers speech, salivation, swallowing, handwriting, handling utensils, dressing and hygiene, turning in bed, walking, climbing stairs, and three measures of respiratory function. Each domain is scored separately, which helps identify which functions are declining fastest. The rate of progression differs widely between individuals. Some people live with manageable symptoms for years, while others experience rapid decline over months.
The combination of symptoms at any given time shapes daily life in concrete ways. Early on, adaptations might be as simple as switching to slip-on shoes or using a thicker pen. As the disease progresses, assistive devices for mobility, communication, and eventually breathing become part of the picture. Understanding which symptoms to watch for, and which functions are likely to remain intact, helps both patients and families plan ahead with realistic expectations.