Question

In December 2004, Mary Lazarro, a 41-year-old mother of two, was admitted to Finger Lakes Community Hospital because of numbness of the chin and lower lip. Two week prior to admission, she noted a prickling sensation like “pins and needles” at the right corner of her mouth. The sensation extended bilaterally to the lower lip and to her chin. Neurologic examination revealed only a superficial hypoesthesia of the chin and lower lip (numb chin syndrome). There was not clinical evidence of palpable regional lymph nodes or other systemic and neurologic abnormalities. X-rays and a CT scan revealed no abnormalities in the jaw, neck, or pharynx. The numbness and hypoesthesia spontaneously disappeared gradually over a few weeks time. 1) The chapter reviews the organization of the human nervous system. From this outline, describe the specific “part” of the nervous system that is affected. 2) Using what you know about the neuroanatomy of this affected region, describe what nerve is involved (hint: this is a complex nerve, so be specific regarding the part that is affected) a. ORIGIN : Where does the nerve originate from? b. COURSE: What is the course of this nerve (what structures does it pass by and/or through?) c. FUNCTION: What is the normal function of this nerve?

Answer 1

Ans :

Your face contains a complex web of nerves. Any sort of damage to one of these nerves can potentially cause numbness in your chin. Depending on which nerve is affected, you may only feel numbness on the right or left side.

In additional to general chin numbness, there’s also a rare condition called numb chin syndrome (NCS). This condition affects the mental nerve, a small sensory nerve that supplies feeling to your chin and lower lip. It typically only affects one side of your chin. NCS can be a serious condition because it’s often associated with certain types of cancer.

Numb chin syndrome (NCS) is a neurological condition that causes numbness in the mental nerve distribution, also known as mental neuropathy. You might feel numbness or a pins and needles sensation in your chin, lips, or gums. Some cases of NCS are related to the teeth, but many have nothing to do with the teeth or dental procedures.

In adults, NCS is often associated with primary breast cancer or lymphoma that’s spread to the jaw. Tumors near your jaw invade or put pressure on the mental nerve, causing neuropathy. It can also be caused by a cancer tumor at the base of the skull.

Introduction. Numb chin syndrome (NCS), often synonymously named as “mental nerve neuropathy,” is a sensory neuropathy characterized by numbness (hypoesthesia, paresthesia, dysesthesia, and anesthesia) or, very rarely, pain of the chin and lower lip within the mental or inferior alveolar nerve distribution.

2. Origin -  The inferior alveolar nerve is a branch of the mandibular nerve. After branching from the mandibular nerve, the inferior alveolar nerve travels behind the lateral pterygoid muscle. It gives off a branch, the mylohyoid nerve, and then enters the mandibular foramen

Course -

The inferior alveolar nerve is a branch of the mandibular nerve. After branching from the mandibular nerve, the inferior alveolar nerve travels behind the lateral pterygoid muscle. It gives off a branch, the mylohyoid nerve, and then enters the mandibular foramen.^[1]:543

While in the mandibular canal within the mandible, it supplies the lower teeth (molars and second premolar) with sensory branches that form into the inferior dental plexus and give off small gingival and dental nerves to the teeth.

Anteriorly, the nerve gives off the mental nerve at about the level of the mandibular 2nd premolars, which exits the mandible via the mental foramen and supplies sensory branches to the chin and lower lip.

The inferior alveolar nerve continues anteriorly as the mandibular incisive nerve to innervate the mandibular canines and incisors

Function -  The inferior alveolar nerves supply sensation to the lower teeth, and, via the mental nerve, sensation to the chin and lower lip. The mylohyoid nerve is a motor nerve supplying the mylohyoid and the anterior belly of the digastric