The commenters nailed it.
He had primary hyperparathyroidism and went for a parathyroidectomy. The recurrent laryngeal nerve was severed during the procedure and that left him unable to speak.
He suffered in silence for 6 months before going for a procedure which pushes the vocal cords on the paralyzed side medially. This allows the normal cord to meet the still paralyzed, but medially displaced cord and phonate.