Head & Neck
51 out of 134
A patient with crocodile tears syndrome has spontaneous lacrimation during eating due to misdirection of regenerating autonomic nerve fibers. Which of the following nerves has been injured
|A||Facial nerve proximal to the geniculate ganglion|
|B||Chorda tympani in the infratemporal fossa|
|C||Facial nerve at the stylomastoid foramen|
Ans. A Facial nerve proximal to the geniculate ganglion
- Crocodile tears syndrome: spontaneous lacrimation occurring parallel with the normal salivation of eating. It follows facial paralysis and is due to inaccurate regrowth of the regenerating nerve fibers into the wrong nerve sheaths, with some of those destined for the salivary glands going to the lacrimal glands.
- Basically the nerve is damaged proximal to geniculate ganglion and the fibres destined to salivary glands & lacrimal glands are damaged. Then in a bid to repair the nerves, fibres regenerate, but are misdirected, sometimes. The salivary fibres move into chorda tympani but also into greater petrosal nerve. Hence, while salivation the tears also flow out !
- Geniculate ganglion (from Latin genu, for "knee"- a bend) is an L-shaped collection of fibers and sensory neurons of the facial nerve located in the facial canal of the head.
- It receives fibers from both the motor, sensory, and parasympathetic components of the facial nerve and sends fibers that will innervate the lacrimal glands, submandibular glands, sublingual glands, tongue, palate, pharynx, external auditory meatus, stapedius, posterior belly of the digastric muscle, stylohyoid muscle, and muscles of facial expression.
- Sensory and parasympathetic inputs are carried into the geniculate ganglion via the nervus intermedius. Motor fibers are carried via the facial nerve proper.
- The greater petrosal nerve, which carries sensory fibers (palatal taste) as well as preganglionic parasympathetic fibers, emerges from the anterior aspect of the ganglion.
- The chorda tympani nerve brings the taste sensations from the tongue into geniculate ganglion
Head & Neck