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BRIEF COMMUNICATIONS: James R. Keane Bilateral involvement of a single cranial nerve: Analysis of 578 cases Neurology 2005; 65: 950-952 [Abstract] [Full text] [PDF]

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Bilateral involvement of a single cranial nerve: Analysis of 578 cases

Alan R Hirsch, MD   (15 November 2005)

Reply to Hirsch et al

James R Keane   (15 November 2005)

Bilateral involvement of a single cranial nerve: Analysis of 578 cases 15 November 2005
Alan R Hirsch, MD, Smell & Taste Treatment and Research Foundation 845 North Michigan Ave., Suite 990W, Chicago, IL 60611 Send Correspondence to journal: Re: Bilateral involvement of a single cranial nerve: Analysis of 578 cases dr.hirsch{at}sbcglobal.net Alan R Hirsch, MD	We read Dr. Keane's article with interest. [1] Dr. Keane’s analysis of the inpatients he personally examined over a thirty-four year period at the Los Angeles County/University of Southern California Medical Center suggested that bilateral involvement of the same cranial nerve is uncommon and is most usually associated with cranial nerve VI damage. However, the most rostral of cranial nerves, the olfactory nerve was not mentioned. Inclusion of this cranial nerve may have substantially changed his results. Bilateral cranial nerve I damage is frequently seen associated with head trauma, including up to 60% of those with severe head injury. Likewise, a variety of other neurologic conditions induce bilateral olfactory deficits including tumors, epilepsy, demyelinating disorder, degenerative disorders including Parkinson’s disease, and Senile Dementia of the Alzheimer’s Type, and migraine [2,3]. Furthermore, inclusion of this cranial nerve would have markedly changed his results since, based on demographics alone, cranial nerve I dysfunction would have been substantial. It is estimated that half of those over the age of 65 and three-quarters of those over the age of 80 have a reduced ability to smell. Furthermore, many medications used in the treatment of neurologic conditions may have also been anticipated to impair his patients’ olfactory ability. The lack of inclusion of cranial nerve I in Dr. Keane’s report highlights the widespread practice of overlooking cranial nerve I in the neurologic examination. In a retrospective study of ninety-four neurology inpatient consultations recorded in the hospital charts, only four had cranial nerve I testing (and those were described as “WNL”) [4]. Since a myriad of neurologic conditions manifest bilateral cranial nerve I dysfunction, and discovery of such loss is important for safety and quality of life. [5] References 1. Keane, JR. Bilateral involvement of a single cranial nerve: Analysis of 578 cases. Neurology, 2005; 65:950-952. 2. Murphy C, Doty RL, Duncan HL. Clinical disorders of olfaction. In: Doty, RL (Ed.). Handbook of Olfaction and Gustation, Second Edition, Revised and Expanded. New York: Marcel Dekker, Inc., 2003. 3. Hirsch AR. Olfaction in migraineurs. Headache, 1992; 32:5:233- 236. 4. Hirsch AR, Colavincenzo ML. Failure of physicians to assess olfactory ability in neurologic inpatients. Chemical Senses, 1999; 24:5:607-608. 5. Hirsch AR. Listening to patients with chemosensory dysfunction. Chicago Medicine, 1998; 101:2:14-17. Disclosure: The authors report no conflicts of interest.
Reply to Hirsch et al 15 November 2005
James R Keane, University of Southern California 1200 N. State Street, Los Angeles, CA 90033 Send Correspondence to journal: Re: Reply to Hirsch et al jkeane{at}usc.edu James R Keane	I agree with the authors on the importance of testing the olfactory nerve. I hope that their letter will be more persuasive than my harangues to residents that the cranial nerves don't begin with II. Disclosure: The author reports no conflicts of interest.