Prior to making the incision, a baseline assessment of background radioactivity is measured by placing the gamma probe over the thyroid isthmus (Fig. 18.2). For this procedure, we use an 11-mm collimated gamma probe (Neoprobe 2000, Ethicon Endo-Surgery Breast Care, Cincinnati, OH). A second background count can be obtained by placing the probe over the left shoulder, if preferred.

Once the background number has been obtained, the incision is made. Dissection is carried down through the platysma, and the straps are divided in the midline if using an anterior approach. For the lateral approach the sternocleidomastoid muscle is separated from the strap and omohyoid muscles.

For those patients who do not have any localization on preoperative imaging, radioactivity counts can be taken on both sides of the neck, or more specifically, the four quadrants of the neck. The area of highest activity gives the surgeon an idea as to where to start dissection.

If the gland is not quickly identified during dissection, the gamma probe can be inserted into the wound to provide the surgeon with a trajectory and area of highest activity to further localize ectopic glands.

Glands identified by the surgeon can then be assessed in vivo for radioactivity over that of baseline (Fig. 18.3). If appearing to be consistent with a diseased gland, the vascular pedicle is isolated and controlled (Fig. 18.4). The specimen is then excised, with the timer starting for intraoperative parathyroid hormone monitoring. Ex vivo counts of the excised gland are taken with the tissue balanced on the tip of the probe to ensure no background is picked up from the patient (Fig. 18.5). Counts greater than 20 % of background are thought to represent pathologic parathyroid tissue and confirm the presence of parathyroid tissue within the specimen. Lymph nodes, fat, and normal parathyroid tissue will not have counts this high.

As the gamma probe only helps localize and then confirm the excision of pathologic tissue, we recommend the concomitant use of intraoperative parathyroid hormone monitoring to confirm that all hyperfunctioning parathyroid tissue has been removed.

Once satisfied that all hyperfunctioning tissue has been excised, hemostasis is meticulously obtained. The wound is then injected with local anesthetic (Fig. 18.6). The strap muscles are then reapproximated, as is the platysma. We use a running, knotless subcuticular closure for the skin (Fig. 18.7a, b). Steri-Strips are then applied.

The majority of patients are able to go home the same day as surgery. Ice packs are routinely used at our institution to minimize tissue swelling and aid in pain control. Oral analgesics are generally all that is needed to achieve adequate pain control. We routinely discharge our patients with oral calcium supplementation. Patients are instructed to take additional doses for any symptoms of hypocalcemia (numbness, tingling, cramping).