The initial, main symptom in<unk>  is painless weakness of specific muscles, not fatigue. The muscle weakness becomes progressively worse during periods of physical activity and improves after periods of rest. Typically, the weakness and fatigue are worse toward the end of the day.<unk>  generally starts with ocular (eye) weakness; it might then progress to a more severe generalized form, characterized by weakness in the extremities or in muscles that govern basic life functions. Eyes In about two-thirds of individuals, the initial symptom of<unk>  is related to the muscles around the eye. Eyelid drooping (ptosis may occur due to weakness of m. levator palpebrae superioris) and double vision (diplopia, due to weakness of the extraocular muscles). Eye symptoms tend to get worse when watching television, reading, or driving, particularly in bright conditions. Consequently, some affected individuals choose to wear sunglasses. The term "ocular<unk> " describes a subtype of<unk>  where muscle weakness is confined to the eyes, i.e. extraocular muscles, m. levator palpebrae superioris, and m. orbicularis oculi. Typically, this subtype evolves into generalized<unk> , usually after a few years. Eating The weakness of the muscles involved in swallowing may lead to swallowing difficulty (dysphagia). Typically, this means that some food may be left in the mouth after an attempt to swallow, or food and liquids may regurgitate into the nose rather than go down the throat (velopharyngeal insufficiency). Weakness of the muscles that move the jaw (muscles of mastication) may cause difficulty chewing. In individuals with<unk> , chewing tends to become more tiring when chewing tough, fibrous foods. Difficulty in swallowing, chewing, and speaking is the first symptom in about one-sixth of individuals. Speaking Weakness of the muscles involved in speaking may lead to dysarthria and hypophonia. Speech may be slow and slurred, or have a nasal quality. In some cases, a singing hobby or profession must be abandoned. Head and neck Due to weakness of the muscles of facial expression and muscles of mastication, facial weakness may manifest as the inability to hold the mouth closed (the "hanging jaw sign") and as a snarling expression when attempting to smile. With drooping eyelids, facial weakness may make the individual appear sleepy or sad. Difficulty in holding the head upright may occur. Other The muscles that control breathing and limb movements can also be affected; rarely do these present as the first symptoms of<unk> , but develop over months to years. In a<unk>  crisis, a paralysis of the respiratory muscles occurs, necessitating assisted ventilation to sustain life. Crises may be triggered by various biological stressors such as infection, fever, an adverse reaction to medication, or emotional stress.
Myasthenia gravis
Guillain–Barré syndrome
Congenital myasthenic syndrome
Botulism
Neurasthenia
Organophosphate poisoning
Polymyositis
Brainstem stroke syndrome