cli nical/scien t ific notes I expedited publication I Vestibular evoked potentials in human neck muscles before and after unilateral vestibular deafferentation J.G. Colebatch, MB, BS, PhD, and G.M. Halrnagyi, MB, BS Current clinical assessment of vestibular function relies heavily upon caloric testing: recording nystagmus caused by hot and cold water irrigation of the ears. The response reflects the integrity of the horizontal canal,' only one of the five vestibular end organs. Furthermore, the nature of caloric testing is such t h a t differences in latency due to central neural conduction delay cannot be detected. Many patients who complain of vestibular symptoms have normal caloric tests. Brainstem potentials following natural stimulation of the horizontal canal are small and require special apparatus capable of rapidly and repeatedly applying high accelerations t o the head.' Attempts a t recording cortical vestibular evoked potentials have given conflicting results.3 We have recently investigated the effects of brief, intense clicks on averaged EMG activity from neck muscles and have identified a short-latency component t h a t is specifically dependent upon t h e integrity of t h e ipsilateral vestibular nerve. The apparatus required is no more complicated than that used in conventional evoked response testing. Case report. A 38-year-old man developed symptoms of Meniere's disease 3 years before presentation. He was troubled by uncontrolled episodes of vertigo, nausea, and tinnitus, and w a s scheduled for selective v e s t i b u l a r n e r v e section. Preoperative testing showed normal caloric responses from both ears. Audiometry showed a 20 dB loss up to 1 kHz, with greater loss a t higher frequencies, and a 20% loss of speech discrimination on the right. An average was made of the effects of 512 presentations (3 per second) of clicks of 0.1-msec duration on surface EMG recorded from over the right and left sternomastoid muscles during a gentle voluntary contraction. The click intensities were referred to the perceptual threshold for normal subjects (= 0 dB). The subject's perceptual thresholds for the clicks were 15 dB (R) and 10 dB (L), and clicks of 100 dB intensity were used for averaging EMG responses. Short-latency, largeamplitude myogenic responses were evoked in both the right and left sternomastoid muscles (figure). The responses began a t an average latency of 8 msec, beginning with a n initial positivity (p13: latency 12.8 msec [R], 12.5 msec IL]), followed by a negativity (1123: latency in this patient 20.6, 20.3 msec) and then a second positivity and negativity.

Before Right Vestibular Nerve Section

The subject was restudied under identical conditions 3 months after selective section of the right vestibular nerve, following which his symptoms had been almost totally relieved. His subjective perceptual thresholds for the clicks were 20 dB (R) and 10 dB (L) above the reference. Retesting showed abolition of the p13-n23 wave previously recorded from the right sternomastoid, with preservation of the later potentials and unaltered responses from the left sternomastoid (figure). Discussion. We have since studied two additional subjects following selective vestibular nerve section with similar results: the p13-n23 wave is present only on the side ipsilateral to the intact vestibular nerve. Conversely, two subjects with sensorineural deafness and elevated perceptual thresholds (thresholds 25 to 80 dB above the reference) but intact caloric responses had p13-n23 evoked responses on both sides. Experiments on animals have shown that clicks similar to the ones we used can activate saccular afferents at short latenC Y . ~Bickford et a15 and Cody and Bickford,fi who pioneered studies of myogenic potentials in human neck muscles, postulated that the effects of loud clicks originated from the vestibular sacculus. We believe that the clicks we used can activate vestibular afferents and thereby reveal short-latency vestibulospinal projections to neck muscles in humans, projections that exist in experimental preparation^.^ The responses shown here a r e probably generated by a vestibular receptor, distinct from the horizontal canal, through a central pathway different from that which mediates the effects of caloric testing. The procedure is sufficiently simple to be done routinely on patients with hearing or balance disorders, and may also provide unique additional information about vestibular function.

Acknowledgment The authors thank Dr. Paul Fagan, FRACS, who kindly referred the patient to us. From the Institute o f Neurological Sciences (Dr. Colebatchi, Prince of Wales Hospital; and the Neuro-Otology Department (Dr. Halmagyii, Royal Prince Alfred Hospital, Sydney, Australia, Supported by a grant from the Cliva and Vera Ramaciotti Foundations Received April 20, 1992. Accepted for publication in final form April 21, 1992. Address correspondence and reprint requests to Dr. J.G. Colebatch, Institute of Neurological Sciences, Prince of Wales Hospital, High Street, Randwick, Sydney 2031, Australia.

References 1. Baloh RW. Honrubia V. Clinical neurophysiology of the

After Right Vestibular Nerve Section R St-m

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Figure. Averaged EMC recorded over neck muscles studied before lleftl and after irighti selective right vestibular nerve section. One-hundred4B clicks were given bilaterally at the time indicated hv the arrows. and 512 responses ;ere averaged. The upper traces show averaged EMG recorded from the right sternomastoid (R St-mi; the lower ones were recorded from the left sternomastoid (L St-nil. Negative potentials at the active electrode are shown upward. Figure shows specific loss of the short-latency positiue-wgative wave, p13-n23, after nerve section on the ipsilateral sid?. Later potentials and nesponses on the left side are unaltered.

August 1992 NEUROLOGY 42 1635

2. Elidan J, Leibner E, Freeman S, Sela M, Nitzan M, Sohmer H. Short and middle latency vestibular evoked responses to acceleration in man. Electroencephalogr Clin Neurophysiol 1991;80:140-145. 3. Durrant JD, Furman JMR. Long-latency rotational evoked potentials i n s u b j e c t s w i t h a n d w i t h o u t b i l a t e r a l v e s t i b u l a r loss. Electroencephalogr Clin Neurophysiol 1988;71:251-256. 4. Didier A, Cazals Y. Acoustic responses recorded from the saccular bundle on the eighth nerve of the guinea pig. Hear Res 1989;37:123-128. 5. Bickford RG, Jacobson J L , Cody DTR. Nature of averaged evoked potentials to sound a n d other stimuli i n man. Ann NY Acad Sci 1964;112:204-223. 6. Cody DTR, Bickford RG. Averaged evoked myogenic responses in normal man. Laryngoscope 1969;79:400-416. 7. Wilson VJ, Yoshida M. Comparison of the effects of stimulation of Deiter's nucleus and medial longitudinal fasciculus on neck, forelimb, and hindlimb motoneurons. J Neurophysiol 1969;32:743-758.

response was obtained from the right (figure). Other nerve conductions i n t h e right lower extremity were normal. Needle examination was also normal. Discussion. The lateral femoral cutaneous nerve usually emerges from the pelvis at the anterosuperior iliac spine passing under the inguinal ligament and supplies the skin over the anterolateral thigh between the hip and knee. Lateral femoral cutaneous neuropathy or meralgia paresthetica most frequently results from tight belts or pants, obesity, ascites, pregnancy, or a n y disorder t h a t increases intra-abdominal pressure and metabolic neuropathies.' In this paper, we report the development of meralgia paresthetica as a result of practicing Siddha yoga. We believe this is the first report of a patient developing this neuropathy from yoga.

Lotus neuropathy: Report of a case

Acknowledgments We thank Lorraine Campione and Diane Burton for manuscript preparation.

Thomas G. Mattio, MD, PhD; Takashi Nishida, MD; and Michael M. Minieka, MD

From the Department of Neurology, Northwestern University Medical School, Chicago, IL.

Siddha yoga meditation is a technique used for relaxation worldwide. Vogel e t all reported the development of sciatic neuropathy in a patient who had been sitting in a modified lotus position. In this paper, we report the development of a lateral femoral cutaneous neuropathy in a patient who had been sitting in the full lotus position. Case report. The patient is a 38-year-old college professor who is a n active practitioner of yoga. He started meditating 15 years ago and has been a daily practitioner for t h e past 10 years. He sits in the lotus position for about 30 minutes per day. The lotus is a standard yoga position in which a person sits with hips flexed and externally rotated, knees bent, legs crossed, and feet resting on the thighs. One month prior to presentation for evaluation, he fell asleep in t h e full lotus position. He was unsure of how long he slept, but stated it was at least 3 hours. When he woke up the next morning, he noticed tingling on the lateral aspect of his right thigh from the inferior border of his hip to the superior aspect of his knee. The tingling was constant, but, after about 24 hours, it stopped and was replaced by numbness. This numbness persisted throughout the month prior to presentation. He denied any weakness in his right leg, back pain, bowel or bladder incontinence, or sexual dysfunction. G e n e r a l physical e x a m i n a t i o n w a s u n r e m a r k a b l e . Specifically, no back pain was elicited with percussion and straight leg lifts were normal. Neurologic examination revealed full strength in hip flexors and all lower extremity muscles bilaterally. Reflexes, tone, bulk, and gait were all normal. Sensory examination revealed loss of pinprick, temperature, and light touch in the distribution of the right lateral femoral cutaneous nerve. An antidromic sensory nerve conduction study was performed, using computer averaging. A normal response was elicited from t h e left lateral femoral cutaneous nerve. No

Y right

1636 NEUROLOGY 42 August 1992

Figure. Antidromic recording of the lateral femoral cutaneous nerve action potential. Each tracing was averaged eight times. Note absent response on the right.

Received November 19, 1991. Accepted for publication in final form January 6, 1992. Address correspondence and reprint requests to Dr. Takashi Nishida, Department of Neurology, Northwestern University Medical School, 233 E. Erie, Chicago, IL 60611.

References 1.Vogel CM, Albin R, Albers JW. Lotus footdrop: sciatic neuropathy in the thigh. Neurology 1991;41:605-606. 2. Williams PH, Trzil KP. Management of meralgia paresthetica. J Neurosurg 1991;74:76-80.

Recurrent aseptic meningitis complicating intravenous immunoglobulin therapy for chronic inflammatory demyelinating polyradiculoneuropathy Mayra Vera-Ramirez, MD; Michael Charlet, MD; and Gareth J . Parry, MD High-dose intravenous immunoglobulin (IVIG) is used in the treatment of many autoimmune diseases, including chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). Contributing to a sense of euphoria concerning its use is the widespread perception t h a t a d v e r s e r e a c t i o n s a r e r a r e . However, a computer-based search of the literature unearthed over 300 references to possible adverse effects, some of them life-threatening. These include major anaphylactic reactions, particularly in individuals with IgA deficiency, hemolysis, hepatitis (non-A, non-B), and even thrombotic events including cerebral infarction.2 One of the most common side effects is headache, which is common during IVIG infusion, particularly at high infusion rates. We now report a patient who developed headache due to aseptic meningitis following each of two courses of IVIG treatment for CIDP. Case report. A 62-year-old woman with progressive, idiopathic CIDP without monoclonal gammopathy was treated with IVIG, 0.4 g/kg/d for 5 consecutive days. The infusion rate was 40 ml during the first hour, 80 ml during the second hour, and 100 ml/hr thereafter. With this regimen, no adverse effects were reported during the treatment period. The day treatment was finished, she developed headache, neck stiffness, fever, nausea, and malaise, which was attributed to influenza and which resolved without specific treatment over the next 3 days. Four months later, she received a second course of IVIG. Infusion was started at 200 mVhr, but she developed headache as well as dyspnea and chest tightness, so the infusion rate was reduced to 100 ml/hr. The symptoms resolved, and she completed this course without further adverse effects. The day treatment was completed, headache, neck stiffness, fever, nausea, and malaise recurred, and she was readmitted 3 days later. At the time of readmission, she was afebrile (temperature,

Vestibular evoked potentials in human neck muscles before and after unilateral vestibular deafferentation J. G. Colebatch and G. M. Halmagyi Neurology 1992;42;1635 DOI 10.1212/WNL.42.8.1635 This information is current as of August 1, 1992 Updated Information & Services

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Neurology ® is the official journal of the American Academy of Neurology. Published continuously since 1951, it is now a weekly with 48 issues per year. Copyright © 1992 by the American Academy of Neurology. All rights reserved. Print ISSN: 0028-3878. Online ISSN: 1526-632X.

Vestibular evoked potentials in human neck muscles before and after unilateral vestibular deafferentation.

cli nical/scien t ific notes I expedited publication I Vestibular evoked potentials in human neck muscles before and after unilateral vestibular deaff...
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