Clinical Case - Eye
A 32 year-old patient presents with septic temperatures, frequent chills, vomiting and intermittent delirium. When lucid, the patient complains of nausea and severe headache, especially on his right side. The patient's case history indicates that he had developed a boil on his right lip six days prior. Earlier in the day, the patient's family physician administered penicillin to the patient. As the patient did not improve, the family physician admitted the patient to the hospital. On physical exam, the patient shows rigidity of his neck muscles, a sign of meningeal irritation. His right cheek , nose and upper lip are swollen and hard to the touch. There is some oozing pus from several points along his upper lip. Extraocular muscle testing shows inability to abduct the right eye. The patient is diagnosed with infectious cavernous sinus thrombosis predicated by staphylococcal infection of the subcutaneous tissue of the upper lip, and partial extraocular paralysis in his right eye.
Questions to consider:
- Why would trauma to the cavernous sinus affect ocular muscle function?The nerves of each eye that control the extraocular muscles travel directly through (abducens nerve), or are in the walls of the respective cavernous sinus (oculomotor and trochlear nerves). Thrombotic congestion and edema could lead to compression damage of the nerves.
- What anatomical structures facilitate the spread of the infection to the cavernous sinus?Since veins are valveless, they allow bi-directional flow. If the blood flowed from the labial vein toward the beginning of the facial vein at the inner angle of the eye, it could then enter the angular vein which communicates with the superior ophthalmic vein, directly draining into the cavernous sinus. Similarly, the infection could have spread from the labial vein to the deep facial vein to the pterygoid plexus directly into the cavernous sinus.
- Discuss a possible course by which the infection spread.See answer to question two above. Also note that the infection could also spread from the right cavernous sinus to the left cavernous sinus via the anterior and posterior intercavernous sinuses.
- Review the innervation to the extraocular muscles. Which nerve and muscle were affected in this patient?The superior oblique muscle is innervated by the trochlear nerve (CN IV). The lateral rectus is innervated by the abducens nerve (CN VI). The oculomotor nerve (CN III) innervates the rest of the extraocular muscles. Since the patient was unable to abduct his right eye, it was his lateral rectus that was paralyzed. The lateral rectus is innervated by the abducens nerve (CN VI).
- If the patient also presented with ptosis, what muscle and nerve are likely affected?The eyelid is held up by the levator palpebrae superioris muscle, which is innervated by the oculomotor nerve. Thus damage to CN III can result in muscle paralysis as well as ptosis. Note that CN III also provides parasympathetic innervation for the sphincter pupillae muscle of the iris and for the ciliary muscle of accommodation.
Clinical Note: Extraocular muscle testing
Since the actions of the extraocular muscles are complex, it is necessary to turn the eye to a position where a single action of each muscle predominates when evaluating the individual muscles. For the superior and inferior recti, turning the eye outward (abduction) by approximately 25 degrees places the superior rectus in position to raise the eye and the inferior rectus to lower the eye. Similarly, turning the eye inward (adduction) approximately 51 degrees places the inferior oblique in position to raise the eye and the superior oblique to lower the eye. The medial and lateral recti may be checked while the eye is staring straight ahead since they have simple planar actions.
A 46-year-old man who had undergone right-sided pneumonectomy for carcinoma of the bronchus was seen by his thoracic surgeon as a follow-up after the operation. The patient said that he felt fit and was gaining some weight. He noticed that a week ago his right upper eyelid tended to droop slightly when he was tired at the end of the day. After a careful physical examination, the surgeon noticed that in addition to the ptosis of the right eye, the patient's right pupil was constricted and that his face was slightly flushed on the right side. Further examination revealed that the skin on the right side of the face appeared to be warmer and drier than normal. Palpation of the deep cervical lymph nodes revealed a large hard fixed node just above the right clavicle. The surgeon made the diagnosis of a right-sided Horner's syndrome which happened as a result of tumor metastasis to the right sympathetic cervical trunk.
- How would you explain the right ptosis and pupillary constriction in this case?
The ptosis is due to the interruption of the sympathetic innervation of the levator palpebrae superioris muscle, which elevates the upper eyelid. Though its major innervation comes from the oculomotor nerve, an injury to its sympathetic innervation will also result in ptosis that is milder and related, as in this case, to the rhythmic activity of the autonomic system. Postganglionic sympathetic fibers to the orbit lie on the surface of the internal carotid artery.
The pupillary constriction results from interruption of sympathetic supply to the dilator pupillae muscle of the iris. The unopposed action of the intact sphinctor pupillae muscle (supplied by parasympathetic innervation from the oculomotor (CN III) nerve will cause pupillary constriction.
The other skin findings in this case could also be explained by interruption of the sympathetic innervation to sweat glands and blood vessels.
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