Amyotrophic Lateral Sclerosis: Where Does Muscle Weakness Begin?

Amyotrophic lateral sclerosis (ALS), commonly known as Lou Gehrig's disease, can begin in various parts of the body. In approximately 60% to 70% of cases, the initial symptoms appear in the hands. Patients often experience difficulty with fine motor skills, such as turning a key, pumping air into a tire, removing a valve stem, or planting rice seedlings.

Early Signs in the Upper Limbs

About half of all ALS patients first notice symptoms in one of their upper limbs. This typically manifests as muscle atrophy in the thenar and hypothenar eminences—the fleshy parts of the palm near the thumb and little finger. Over time, the muscle wasting may extend to the forearm and eventually reach the upper arm, pectoral muscles, back, and even the calves. This progressive weakening can occur with or without increased muscle tone and is often accompanied by muscle twitching and impaired mobility.

Less Common Onset: Bulbar Symptoms

In a smaller percentage of cases, ALS begins in the bulbar region, which controls speech and swallowing. Early symptoms may include slurred speech, difficulty articulating words clearly, a nasal tone, or choking while drinking water. These signs are often mistaken for a common throat infection, leading patients to consult ear, nose, and throat specialists before receiving a correct diagnosis.

Disease Progression and Patterns

Among the different patterns of onset, limb involvement—especially in the upper limbs—is the most frequent. Less commonly, the disease begins in the lower limbs or in the bulbar region. The least common form of onset is thoracic, meaning it starts in the chest muscles. Regardless of where ALS begins, the condition progressively spreads, eventually affecting most major muscle groups throughout the body.