Diagnosis

Nerve Blocks:

What is a Nerve Block?

A Nerve Block is a procedure that disrupts specific nerve activity. It can help diagnose or treat certain types of neuropathic loss or alteration of smell or taste, or smell and taste disorders caused by nerve dysfunction or damage. Nerve blocks may be performed by injecting anesthetics or chemicals to the area, or by deliberately cutting or damaging certain parts of the nerve.

The Nerve Block procedure is performed by physician to anesthetize or numb a particular nerve in the body to diagnose or treat certain form of nerve disorder. The procedure involves the injection of a local anesthetic (like Lidocaine or Bupivicaine) or chemicals onto a target nerve or group of nerves. An example of a diagnostic nerve block is the glossopharyngeal nerve (innervating taste buds at the back of the tongue) block, performed to diagnose phantom taste. The local anesthetic works by interrupting conduction of electrical impulses along the target nerve for a limited period of time. The duration of the numbing effect varies with the local anesthetic used.

What is a Diagnostic Chemosensory Nerve Block?

A Diagnostic Chemosensory Nerve Block involves numbing a specific nerve or group of nerves that may be involved in certain forms of chemosensory (smell and taste) disorders. The physician performing the nerve block is an expert in anatomy so that he/she knows the location of various carrying nerves. A local anesthetic is injected in very small amounts onto target nerves, and the patient is then assessed for any change in chemosensory symptoms. If a particular carrying nerve or group of nerves is/are numbed and a patient notes significant improvement in their chemosensory symptoms, the location of the symptom generator is likely confirmed. If a patient notes no change or limited change in chemosensory symptoms following a diagnostic nerve block, the treating physician may conclude that a patient’s chemosensory symptoms is originating from a different area.

Why is a Diagnostic Nerve Block Used in the Treatment of Chemosensory Disorders?

One of the most important aspects to the treatment of chemosensory disorders, is the identification of the underlying cause of the chemosensory symptoms or the chemosensory symptom generator. For many forms of chemosensory symptoms, especially in taste dysfunction, there can be significant overlap or similarity in the symptoms produced by the chemosensory symptom generators. For example, dysgeusia (distorted ability to taste) can originate from at least several different sources, including chorda tympany branch of the facial nerve (innervating taste buds on the front of the tongue), lingual branch of the glossopharyngeal nerve (innervating taste buds at the back of the tongue), and nerve endings of the trigeminal nerve that project into the papillae and other oral mucosa surfaces (where they signal sensations of touch, pain, and temperature – other components of flavor - e.g., the fizziness of carbonated drinks and the warmth of coffee). The treatment for each of these nerves can be quite different, so it is very important to identify the chemosensory symptom generator. A Diagnostic Nerve Block is used to confirm the location of the chemosensory symptom generator(s) and the nerve(s) carrying impulses from these structures. Once identified, the chemosensory symptom generator can be treated with a variety of interventional treatments including repeated nerve blocks with anesthetic or other chemicals.

A patient is not sedated for a diagnostic nerve block procedure because he/she must be able to provide reliable information regarding any change in chemosensory symptoms immediately during and after the procedure. Although a diagnostic nerve block sounds like it might be painful, this technique is very well tolerated by adult patients of all ages.

What Should I Do to Prepare for My Procedure?

You should not eat or drink anything at all for at least eight (8) hours before your scheduled procedure. You must have a responsible adult available to drive you home. If you usually take medication for high blood pressure or any kind of heart condition, it is very important that you take this medication at the usual time with a small sip of water before your procedure.

If you are taking any type of medication that can thin the blood and cause excessive bleeding, you should inform our clinic and discuss with your other doctors (PCP, Cardiologist) whether to discontinue this medication prior to the procedure. Examples of medications that could promote surgical bleeding include Coumadin, Plavix, Aggrenox, Pletal, Ticlid, and Lovenox. Anticoagulant medications are usually prescribed to protect a patient against stroke, heart attack, or other vascular occlusion event. Therefore, the decision to discontinue one of these medications is not made by the Smell and Taste Clinic physician but by the primary care or specialty physician (cardiologist) who prescribes and manages that medication.

Could There be Side Effects or Complications?

Modern medicine has improved safety with every aspect of patient care, but there is no guarantee of a perfect outcome with any test or procedure. Fortunately the side effects and complication profile for a Diagnostic Nerve Block is very low. There may be some temporary discomfort in the area of injection, but this will improve within few days or sooner. The doctor will discuss this issue with you before the procedure.

What Should I Do After a Diagnostic Nerve Block Procedure?

Immediately after this procedure, the clinic staff will question you to determine if there has been a change in your chemosensory symptoms. You will be asked to perform activities that will provoke your typical chemosensory symptoms. You will also be asked to provide a numerical chemosensory symptom score every few minutes until you leave the clinic. The information that you provide regarding the presence or absence of the chemosensory symptoms as well as its intensity will be used to formulate a treatment plan. You will also be given a form so that you can continue to record your chemosensory symptom score at home every day after arrival home. You should be able to return to work or your usual daily routine the next day.