The causes of numbness in the left thumb are mainly the following: 1, there may be neurogenic cervical spondylosis, which is due to herniated discs or cervical spine areas with significant stenosis, hyperplasia, stimulation of nerve roots, resulting in nerve fiber ischemia, there will be obvious symptoms of numbness in the distal nerve distribution area, when the top of the head pressure will lead to increased stimulation of local nerves, which will lead to increased numbness 2, thoracic orifice syndrome or cervical rib or oblique angle muscle syndrome, these will form local hyperplasia, edema and adhesion tissue, which will produce extrusion stimulation to the nerve penetration location, which will also lead to decreased blood supply to the nerve, resulting in symptoms of numbness in the distal end. 3, it may be due to stimulation of the median or radial nerve, such as muscle tissue strain, strain, inflammation, hyperplasia, calcification, etc., which may stimulate The nerve fiber bundle, and the symptoms of distal numbness appear.