[ns] Meningioma
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THE NERVOUS SYSTEM
Meningioma
A 52-year-old woman noticed a gradual loss of vision in both eyes, and she experienced progressively severe headaches. A careful examination by her physician revealed that her right optic disc was pale and that she had a central scotoma on the right side. The margin of the left optic disc was blurred, the central veins of the retina were dilated, and the optic disc protruded by 2 diopters from the surface of the retina. Some hemorrhages and exudates were noted in the retina around the optic disc. On further testing the patient could not recognize odors introduced into her right nostril, but her sense of smell was intact on the left. 1. Why was the patient unable to recognize odors in the right nostril? 2. What is a possible cause for this malfunction? 3. What caused the central scotoma in the right eye? 4. What is wrong with the left eye? What has caused this? 5. Can anything be done for the patient? What residual deficits are likely after successful treatment?
1. The olfactory pathway on the right side has been interrupted, causing a unilateral anosmia.
2. Because the disease apparently progressed relatively slowly, there is a strong possibility that the underlying problem is a brain tumor. A massive lesion, such as a meningioma in the olfactory groove, could explain the anosmia, because it might well compress the olfactory tract. If the tumor grew further, it could also affect the left olfactory tract and cause bilateral anosmia. The headaches are likely to be secondary to an increased intracranial pressure.
3. The central scotoma in the right eye is caused by pressure on the right optic nerve, which passes close to the olfactory tract en route to the optic chiasm. Many axons of the right optic nerve must have been interrupted to cause the optic disc to become pale after Wallerian degeneration, with the consequent loss of myelin.
4. The changes observed in the left eye are typical of papilledema. This condition can result from an increase in intracranial pressure. The pressure is transmitted directly through the cerebrospinal fluid in the subarachnoid space to the optic disc; this occurs because the optic nerves are ensheathed by the meninges and are surrounded by a subarachnoid space at their origin from the optic disc. Pressure here will tend to cause venous stasis and edema in the optic nerve head.
5. If the lesion is an olfactory groove meningioma, this type of brain tumor can often be cured by surgical removal. However, it is unlikely that the patient will recover from the deficit in olfaction or the central scotoma, because axons in the affected neural structures have already been permanently lost.
Meningioma
A 52-year-old woman noticed a gradual loss of vision in both eyes, and she experienced progressively severe headaches. A careful examination by her physician revealed that her right optic disc was pale and that she had a central scotoma on the right side. The margin of the left optic disc was blurred, the central veins of the retina were dilated, and the optic disc protruded by 2 diopters from the surface of the retina. Some hemorrhages and exudates were noted in the retina around the optic disc. On further testing the patient could not recognize odors introduced into her right nostril, but her sense of smell was intact on the left. 1. Why was the patient unable to recognize odors in the right nostril? 2. What is a possible cause for this malfunction? 3. What caused the central scotoma in the right eye? 4. What is wrong with the left eye? What has caused this? 5. Can anything be done for the patient? What residual deficits are likely after successful treatment?
1. The olfactory pathway on the right side has been interrupted, causing a unilateral anosmia.
2. Because the disease apparently progressed relatively slowly, there is a strong possibility that the underlying problem is a brain tumor. A massive lesion, such as a meningioma in the olfactory groove, could explain the anosmia, because it might well compress the olfactory tract. If the tumor grew further, it could also affect the left olfactory tract and cause bilateral anosmia. The headaches are likely to be secondary to an increased intracranial pressure.
3. The central scotoma in the right eye is caused by pressure on the right optic nerve, which passes close to the olfactory tract en route to the optic chiasm. Many axons of the right optic nerve must have been interrupted to cause the optic disc to become pale after Wallerian degeneration, with the consequent loss of myelin.
4. The changes observed in the left eye are typical of papilledema. This condition can result from an increase in intracranial pressure. The pressure is transmitted directly through the cerebrospinal fluid in the subarachnoid space to the optic disc; this occurs because the optic nerves are ensheathed by the meninges and are surrounded by a subarachnoid space at their origin from the optic disc. Pressure here will tend to cause venous stasis and edema in the optic nerve head.
5. If the lesion is an olfactory groove meningioma, this type of brain tumor can often be cured by surgical removal. However, it is unlikely that the patient will recover from the deficit in olfaction or the central scotoma, because axons in the affected neural structures have already been permanently lost.
