Inflammation in the upper neck can cause radiculopathy by constraining blood flow to the nerves or restricting nerve signals. This can cause numbness. Inflammation can also cause restricted blood flow to the brain stem resulting in numbness or weak nerve response because the nerve processing center is not functioning at full capacity. This can also manifest as autonomic disregulation.

There are nerve conduction tests (EMG Electromyography, ENG Electroneurography) that test nerve signals up the arms and legs. But, the tests to measure peripheral nerve signals to the brain are less common. Somatosensory evoked potentials (SEP) can measure the brain's response to peripheral sensations like touch. An SEP when you are most symptomatic would be interesting. But, trying to resolve upper neck inflammation issues would be a good start.