Chiari malformation is caused by the low position of the cerebellar tonsils (the lowermost protrusions of the cerebellum, one on each side, with a shape very similar to the tonsils of the throat), which cause compression of the medulla oblongata and the upper cervical spinal cord, and pulling on the surrounding cranial nerves and cervical nerves, as well as the spinal cord cavity (which can be interpreted as fluid accumulation in the spinal cord), resulting in the corresponding clinical symptoms. Specific symptoms include: muscle weakness, mainly in the upper extremities, but in severe cases also in the lower extremities; focal atrophy, mainly in the large and small interosseous muscles on both sides of the hand; muscle spasm, mainly in the upper extremities and hands, often manifested as difficulty in extending the arms and fingers, and in severe cases the lower extremities can also be involved; sensory disturbances, typically with reduced pain-temperature sensation and normal tactile sensation in one or both upper extremities; dysphagia/choking and coughing with water; dyspnea vertigo; nystagmus; gait instability/ataxia (decreased balance and coordination); little or no sweating on half of the body or face; neck pain; limited neck movement; and neck torsion.