DENTAL GROSS ANATOMY CASE 2.2

HISTORY A 62-year old woman complained to her dentist about sudden bouts of excruciating pain on the left side of her face. The bouts had started ~ 2 months previously and had been increasing in severity. The stabbing pains lasted 15-20 seconds, occurred several times a day and were so severe that she had once contemplated suicide. After examination the dentist told her there was no dental cause for the pain and he referred her to a physician.

PHYSICAL EXAMINATION The woman told the physician that the onset of the pain was sometimes triggered by chewing or a cold wind blowing on her upper lip. When asked to point out the area where the pain occurred she pointed to her left upper lip and cheek. She indicated that the pain also radiated to her lower eyelid, lateral side of the nose and the inside of the mouth. The physician applied firm pressure over the patient’s left cheek and over her infraorbital area, but detected no tenderness indicative of maxillary sinusitis. The physician did detect acute sensitivity to touch on the left upper lip and to pin-pricking over the entire left maxillary region. No abnormality of sensation was found in the forehead or mandibular regions.

1. What is the diagnosis? What is the diagnosis? Trigeminal neuralgia (tic douloureux). The term “tic” (twitch) derives from the fact that the patient winces because of the intense pain.

TRIGEMINAL NEURALGIA (“TIC DOULOUREUX”) This patient is typical as far as age, sex and involved distribution of the trigeminal nerve is concerned. Thus, the disease is more common in the elderly female.

2. Which branch of what major nerve supplies the area of skin and mucous membrane where the paroxysms (sudden recurring attacks) of stabbing pain were felt? Which branch of what major nerve supplies the area of skin and mucous membrane where the paroxysms (sudden recurring attacks) of stabbing pain were felt? Maxillary branch of the trigeminal nerve (V2). Trigeminal neuralgia usually involves V2 (V3 less frequently, V1 least frequently).  

Maxillary n. (V2)

Infraorbital n. Zygomaticofacial n. Zygomaticotemporal n.

Through what foramen and what bone does this nerve leave the skull?   Through the foramen rotundum in the greater wing of the sphenoid bone.

Greater wing of sphenoid Foramen rotundum (for V2)

Why was no abnormality of sensation found in the forehead region? In the mandibular region? Why was no abnormality of sensation found in the forehead region? In the mandibular region? Because sensation in the forehead and mandibular regions is mediated via the ophthalmic (V1) and mandibular (V3) branches of the trigeminal nerve, respectively.  

Ophthalmic n. (V1) Maxillary n. (V2) Mandibular n. (V3)

Where are the cell bodies of the affected nerve located? In the trigeminal ganglion, which lies in a depression on the apex of the petrous part of the temporal bone in the middle cranial fossa.  

Trigeminal ganglion

Depression for V ganglion (in petrous temporal bone)

6. Why were no motor deficits observed in this patient? Because V2 is purely sensory (as is V1). Only V3 contains motor fibers (to the muscles of mastication, etc.).

Mesencephalic nucleus of V (proprioceptive) Sensory root Mesencephalic nucleus of V (proprioceptive) V1 Pontine sensory nucleus of V (fine touch) V2 V3 Motor nucleus of V (mm of mastication,etc.) Motor root Spinal nucleus of V (pain, temperature) Motor fibers Sensory fibers

SENSORY AND MOTOR ROOTS OF V Midbrain ANTERIOR V1 V2 V ganglion Motor root of V V nerve cut & reflected Sensory root of V

What may be the cause(s) of this condition? Usually the cause of the neuralgia is unknown. However, the following causes have been suggested by various investigators: 1) Inflammation of the petrous part of the temporal bone (osteitis). (Note: This is understandable in view of the location of the trigeminal ganglion—see #5 above.) 2) Presence of an aberrant artery that lies close to the sensory root of V and compresses it. 3) A pathological process affecting neurons in the trigeminal ganglion or nucleus of the spinal tract of V.

Usually the cause of trigeminal neuralgia is unknown.

INFECTION OF APEX OF PETROUS TEMPORAL BONE

COMPRESSION OF SENSORY ROOT OF V BY AN ABERRANT ARTERY Usually a branch of the superior cerebellar a. forms an aberrant loop that can compress the sensory root of V. (Netter’s Neurology, p. 106)

Pathological process involving cells of the V ganglion or spinal nucleus of V

How might this condition be treated? Several treatments are possible, including partial cutting of the sensory root of V (rhizotomy) between the trigeminal ganglion and the brainstem. In this procedure, fibers of V2 or V3 are cut, thus eliminating the sensations of pain, temperature and touch in their respective areas of distribution. (V1 fibers are spared because destruction of the sensory fibers from the cornea leads to abolishment of the protective corneal reflex. The absence of this reflex makes the cornea susceptible to inflammation and ulceration due to dessication and trauma, with possible loss of eyesight.)

Medications can be used to treat this condition. These drugs increase the threshold to neural stimulation.

DECOMPRESSION OF SENSORY ROOT OF V

PERCUTANEOUS RADIOFREQUENCY RHIZOTOMY OF SENSORY ROOT OF V Partial rhizotomy of sensory root of V Information from Netter’s Neurology (p. 106). 1. These two procedures result in partial and irreversible destruction of the sensory root and trigeminal ganglion. Trigeminal ganglion PERCUTANEOUS BALLOON COMPRESSION OF TRIGEMINAL GANGLION

ADDITIONAL NOTE It is noteworthy that the patient first consulted her dentist about her problem and that her physician examined her for possible maxillary sinusitis. Under the mistaken belief that the pain of trigeminal neuralgia is due to dental disease or sinusitis, patients have had upper teeth extracted and their maxillary sinuses drained, but with no relief.

MAXILLARY NERVE (V2) V1 V ganglion Sensory root of V Infraorbital n. Anterior superior alveolar n. V3 V2 Mucosa of maxillary sinus Dental and gingival branches Middle superior alveolar n. Posterior superior alveolar n.

END OF CASE 2.2

TIME 2011 (DS-1): ~ 40 MIN. (Good discussion/interaction with class; felt it was worthwhile to spend extra time and discuss details in this case). 2012 (DS-1): 25-30 min.