Vestibular Neuritis, or Driving Dizzily through Donegal
http://www.100md.com
《新英格兰医药杂志》
Ten years ago, while touring the west coast of Ireland, I had a sudden onset of vertigo without hearing loss, tinnitus, or fullness in an ear. As a neurologist, I did entertain fleeting dark thoughts of a fatal basilar occlusion or brain-stem tumor. But without accompanying neurologic symptoms, the obvious diagnosis was vestibular neuritis — a disorder then thought to have a "viral" cause and a benign course. Therefore, I took no medications, abdicated the driving to my wife, and leaned back for several days of unsteadiness. I had full confidence that central compensation would allow for my rapid adaptation to even complete vestibular paresis. I was wrong about the natural course of the disease, and I may have been wrong about the treatment.
Old textbooks incorrectly stated that the symptoms of vestibular neuritis resolve within a few days or weeks. Rapid central compensation or peripheral recovery does occur and is sufficient to cause patients to stop complaining to their doctors. But when asked directly about residual symptoms months or even years later, more than half of patients report minor symptoms such as vertigo with sudden movement of the head, imbalance in the dark, or as in my case, inability to walk across a log spanning a moving stream.
What do we know now about the cause of vestibular neuritis and its persistent symptoms? It is still thought that the syndrome of vertigo without auditory symptoms results from inflammation in the vestibular nerve and, in many patients, from permanent damage to the semicircular canals. A viral cause is assumed, since the results of the limited pathological studies that have been performed long after neuritis has resolved resemble those in patients who have had viral infections. But unlike the studies of deafness that accompanies mumps virus, cytomegalovirus, and measles virus infections of the labyrinth, in which virus has been recovered from the perilymph or characteristic cytopathological features or viral antigens have been found in labyrinthine cells, the data implicating any virus as a cause of vestibular neuritis are circumstantial and conflicting.
Two different modes of viral injury have been proposed. First, primary infections with a variety of respiratory agents may cause vestibular neuritis — a theory based on observations that cases tend to be seasonal and often cluster, even within families, and that about half of patients have a history of respiratory symptoms preceding the vertigo. This hypothesis assumes that the syndrome is caused by a number of viruses — making it analogous to aseptic meningitis, which has been linked to about 100 viruses. This scenario is supported by limited seroepidemiologic data implicating herpes simplex virus (HSV), cytomegalovirus, Epstein–Barr virus, rubella virus, adenoviruses, and influenza A and B viruses in episodes of vestibular neuritis.1
The second hypothesis is that disease is related to the activation of latent HSV type 1 — a theory built on an analogy to some cases of Bell's palsy, in which HSV has been recovered from endoneural fluid at the time of attacks. This thesis is supported by the finding that HSV is often latent in cranial ganglia including the vestibular ganglia, but activation at the time of disease has not been documented in vestibular neuritis as it has in Bell's palsy. Also, experimental studies in which viruses have been inoculated directly into the labyrinth have shown that HSV can infect the neuroepithelium of the semicircular canals,2,3 but no recovery of a herpesvirus and no demonstration of the presence of inclusion bodies or viral antigen in specimens from humans have been reported. These findings support the biologic plausibility that the activation of HSV may cause disease but are not consistent with the epidemiologic observations of seasonal and geographic clustering.
In the past, some physicians have prescribed corticosteroids for the short-term treatment of vestibular neuritis, with the rationale that swelling within the nerve or ganglia might be tempered. Although it makes sense that the reduction of inflammation and edema by corticosteroids might hasten recovery or even minimize permanent damage, good data to support their use have been lacking.
In this issue of the Journal, Strupp et al. (pages 354–361) report the results of a randomized trial in which corticosteroids and antiherpesvirus medication were used to treat vestibular neuritis in an effort to reduce long-term vestibular dysfunction. The use of corticosteroids during the acute episode of vertigo, with or without the administration of the antiviral drug valacyclovir, clearly improved caloric responses as tested one year later. The outcome after treatment with the antiviral drug alone, however, was no better than that after placebo, and the combination of the antiviral drug with corticosteroids showed no advantage over corticosteroids alone.
Do the present findings provide strong evidence against a role of HSV in vestibular neuritis? The authors speculate that viral replication and damage might already have occurred by the time the antiviral drug was administered. Alternatively, I would suggest, the drug may have been ineffective because HSV may not be involved or may represent only one of many causes of vestibular neuritis, so that any beneficial effects of valacyclovir would be so diluted as to be undetectable.
The report by Strupp et al. documents clearly that the treatment of acute vestibular neuritis with corticosteroids results in improved caloric responses one year later. However, a recent clinical follow-up study showed that residual deficits in peripheral vestibular responses seven or eight years after vestibular neuritis did not correlate with residual symptoms.4 Further study is needed to assess whether corticosteroid treatment affects how the patient feels in the long term.
Had these data been available to me a decade ago, would I have behaved differently? I am not certain, but I guess I would have taken corticosteroids for a few days while driving up the coast of Donegal. Maybe — but only maybe — I would now be free of the minor irritations of occasional unsteadiness with sudden turns of the head and, more important, be able to cross streams in the woods with dry feet.
Source Information
From the Johns Hopkins University School of Medicine and Bloomberg School of Public Health, Baltimore.
References
Hirata T, Sekitani T, Okinaka Y, Matsuda Y. Serovirological study of vestibular neuronitis. Acta Otolaryngol Suppl 1989;468:371-373.
Davis LE, Johnsson L-G. Viral infections of the inner ear: clinical, virological, and pathologic studies in humans and animals. Am J Otolaryngol 1983;4:347-362.
Davis LE, Shurin S, Johnson RT. Experimental viral labyrinthitis. Nature 1975;254:329-331.
Bergenius J, Perols O. Vestibular neuritis: a follow-up study. Acta Otolaryngol (Stockh) 1999;119:895-899.(Richard T. Johnson, M.D.)
Old textbooks incorrectly stated that the symptoms of vestibular neuritis resolve within a few days or weeks. Rapid central compensation or peripheral recovery does occur and is sufficient to cause patients to stop complaining to their doctors. But when asked directly about residual symptoms months or even years later, more than half of patients report minor symptoms such as vertigo with sudden movement of the head, imbalance in the dark, or as in my case, inability to walk across a log spanning a moving stream.
What do we know now about the cause of vestibular neuritis and its persistent symptoms? It is still thought that the syndrome of vertigo without auditory symptoms results from inflammation in the vestibular nerve and, in many patients, from permanent damage to the semicircular canals. A viral cause is assumed, since the results of the limited pathological studies that have been performed long after neuritis has resolved resemble those in patients who have had viral infections. But unlike the studies of deafness that accompanies mumps virus, cytomegalovirus, and measles virus infections of the labyrinth, in which virus has been recovered from the perilymph or characteristic cytopathological features or viral antigens have been found in labyrinthine cells, the data implicating any virus as a cause of vestibular neuritis are circumstantial and conflicting.
Two different modes of viral injury have been proposed. First, primary infections with a variety of respiratory agents may cause vestibular neuritis — a theory based on observations that cases tend to be seasonal and often cluster, even within families, and that about half of patients have a history of respiratory symptoms preceding the vertigo. This hypothesis assumes that the syndrome is caused by a number of viruses — making it analogous to aseptic meningitis, which has been linked to about 100 viruses. This scenario is supported by limited seroepidemiologic data implicating herpes simplex virus (HSV), cytomegalovirus, Epstein–Barr virus, rubella virus, adenoviruses, and influenza A and B viruses in episodes of vestibular neuritis.1
The second hypothesis is that disease is related to the activation of latent HSV type 1 — a theory built on an analogy to some cases of Bell's palsy, in which HSV has been recovered from endoneural fluid at the time of attacks. This thesis is supported by the finding that HSV is often latent in cranial ganglia including the vestibular ganglia, but activation at the time of disease has not been documented in vestibular neuritis as it has in Bell's palsy. Also, experimental studies in which viruses have been inoculated directly into the labyrinth have shown that HSV can infect the neuroepithelium of the semicircular canals,2,3 but no recovery of a herpesvirus and no demonstration of the presence of inclusion bodies or viral antigen in specimens from humans have been reported. These findings support the biologic plausibility that the activation of HSV may cause disease but are not consistent with the epidemiologic observations of seasonal and geographic clustering.
In the past, some physicians have prescribed corticosteroids for the short-term treatment of vestibular neuritis, with the rationale that swelling within the nerve or ganglia might be tempered. Although it makes sense that the reduction of inflammation and edema by corticosteroids might hasten recovery or even minimize permanent damage, good data to support their use have been lacking.
In this issue of the Journal, Strupp et al. (pages 354–361) report the results of a randomized trial in which corticosteroids and antiherpesvirus medication were used to treat vestibular neuritis in an effort to reduce long-term vestibular dysfunction. The use of corticosteroids during the acute episode of vertigo, with or without the administration of the antiviral drug valacyclovir, clearly improved caloric responses as tested one year later. The outcome after treatment with the antiviral drug alone, however, was no better than that after placebo, and the combination of the antiviral drug with corticosteroids showed no advantage over corticosteroids alone.
Do the present findings provide strong evidence against a role of HSV in vestibular neuritis? The authors speculate that viral replication and damage might already have occurred by the time the antiviral drug was administered. Alternatively, I would suggest, the drug may have been ineffective because HSV may not be involved or may represent only one of many causes of vestibular neuritis, so that any beneficial effects of valacyclovir would be so diluted as to be undetectable.
The report by Strupp et al. documents clearly that the treatment of acute vestibular neuritis with corticosteroids results in improved caloric responses one year later. However, a recent clinical follow-up study showed that residual deficits in peripheral vestibular responses seven or eight years after vestibular neuritis did not correlate with residual symptoms.4 Further study is needed to assess whether corticosteroid treatment affects how the patient feels in the long term.
Had these data been available to me a decade ago, would I have behaved differently? I am not certain, but I guess I would have taken corticosteroids for a few days while driving up the coast of Donegal. Maybe — but only maybe — I would now be free of the minor irritations of occasional unsteadiness with sudden turns of the head and, more important, be able to cross streams in the woods with dry feet.
Source Information
From the Johns Hopkins University School of Medicine and Bloomberg School of Public Health, Baltimore.
References
Hirata T, Sekitani T, Okinaka Y, Matsuda Y. Serovirological study of vestibular neuronitis. Acta Otolaryngol Suppl 1989;468:371-373.
Davis LE, Johnsson L-G. Viral infections of the inner ear: clinical, virological, and pathologic studies in humans and animals. Am J Otolaryngol 1983;4:347-362.
Davis LE, Shurin S, Johnson RT. Experimental viral labyrinthitis. Nature 1975;254:329-331.
Bergenius J, Perols O. Vestibular neuritis: a follow-up study. Acta Otolaryngol (Stockh) 1999;119:895-899.(Richard T. Johnson, M.D.)