common Metachromatic leukodystrophy Rett syndrome Spinal muscular atrophy Infections Encephalitis Guillain–Barré syndrome Infant botulism Meningitis Poliomyelitis Sepsis Toxins Infantile acrodynia (childhood mercury poisoning) Autoimmunity disorders Myasthenia gravis – most common Abnormal vaccine reaction Celiac disease Metabolic disorder Hypervitaminosis Kernicterus Rickets Neurological Traumatic brain injury, such as the damage that is caused by shaken baby syndrome Lower motor neuron lesions Upper motor neuron lesions Miscellaneous Central nervous system dysfunction, including cerebellar lesions and cerebral palsy Hypothyroidism Sandifer syndrome Neonatal benzodiazepine withdrawal syndrome in children born to mothers treated in late pregnancy with benzodiazepine medications Diagnosis The approach to diagnosing the cause of hypotonia (as with all syndromes in neurology) is first localization. The physician must first determine if the hypotonia is due to muscle, neuromuscular junction, nerve, or central cause. This will narrow the possible causes. If the cause of the hypotonia is found to lie in the brain, then it can be classified as a cerebral palsy. If the cause is localized to the muscles, it can be classified as a muscular dystrophy. If the cause is thought to be in the nerves, it is called hypotonia due to polyneuropathy. Many cases cannot be definitively diagnosed. Diagnosing a patient includes obtaining family medical history and a physical examination, and may include such additional tests as computerized tomography (CT) scans, magnetic resonance imaging (MRI) scans, electroencephalogram (EEG), blood tests, genetic testing (such as chromosome karyotyping and tests for specific gene abnormalities), spinal taps, electromyography muscle tests, or muscle and nerve biopsy. Mild or benign hypotonia is often diagnosed by physical and occupational therapists through a series of exercises designed to assess developmental progress, or observation of physical interactions. Since a hypotonic child has difficulty deciphering their spatial location, they may have some recognizable coping mechanisms, such as locking the knees while attempting to walk. A common sign of low-tone infants is a tendency to observe the physical activity of those around them for a long time before attempting to imitate, due to frustration over early failures. Developmental delay can indicate hypotonia. MRI Brain is used to rule out structural malformations in the brain or metabolic disorders. Magnetic resonance spectroscopic imaging is used to detect metabolic disorders. Treatment The outcome in any particular case of hypotonia depends largely on the nature of the underlying disease. In some cases, the underlying cause is treatable. But in general, treatment comprises providing supportive care with