What Causes Numbness In Lips And Fingertips While Having Ganglion Cyst In Left Wrist?

I have numbness in my lips and fingertips, generally thumb and index finger only. Occurs only on one side at a time, but generally the left. No weakness or pain in arms. No vision loss or facial numbness or weakness. No real dizziness. I do have a ganglion cyst on left wrist.