Advanced Arab Academy of Audio-Vestibulogy Journal

ORIGINAL ARTICLE
Year
: 2015  |  Volume : 2  |  Issue : 1  |  Page : 28--38

Evaluation of dizzy adult patients using the Arabic dizziness questionnaire and its correlation with different vestibular test results


Mohamed T Ghannoum, Mona H Selim, Mohamed S Elminawi, Mariam M Medhat 
 Department of Otolaryngology, Audiology Unit, Kasr Al-Ainy Faculty of Medicine, Cairo University, Cairo, Egypt

Correspondence Address:
Mariam M Medhat
Audiology Unit, Department of Otolaryngology, Kasr Al-Ainy Faculty of Medicine, Cairo University, Cairo
Egypt

Abstract

Objectives The aim of this study was to develop an Arabic dizziness questionnaire for adults and compare the questionnaire conclusion with the results of vestibular evaluation. Participants and methods Twenty dizzy adults, age 21-60 years, were subjected to an interview with patients using the Arabic dizziness questionnaire, otological examination, bedside examination for dizzy patients, basic audiological evaluation, and vestibular assessment, which included the following: videonystagmography, cervical vestibular-evoked myogenic potentials, and sensory organization testing through dynamic posturography. Parameters under study were questionnaire scores and conclusion, videonystagmography results including canal paresis, and cervical vestibular-evoked myogenic potentials latency, amplitude, and threshold. Sensory organization testing result analysis in the form of equilibrium scores and sensory analysis. Results Comparisons and correlations between the vestibular score of the questionnaire and results of the vestibular assessment were nonstatistically significant. The most common diagnoses for dizziness in the adult group were vestibular neuritis (four cases), Mιniθre�SQ�s disease (four cases), benign paroxysmal positional vertigo (three cases), and migraine-associated dizziness (three cases). Conclusion Adult patients sharing the same diagnosis consistently answered certain questions positively in the questionnaire. We recommend the use of the dizziness questionnaire as a first step of the test battery for the evaluation of dizzy patients.



How to cite this article:
Ghannoum MT, Selim MH, Elminawi MS, Medhat MM. Evaluation of dizzy adult patients using the Arabic dizziness questionnaire and its correlation with different vestibular test results.Adv Arab Acad Audio-Vestibul J 2015;2:28-38


How to cite this URL:
Ghannoum MT, Selim MH, Elminawi MS, Medhat MM. Evaluation of dizzy adult patients using the Arabic dizziness questionnaire and its correlation with different vestibular test results. Adv Arab Acad Audio-Vestibul J [serial online] 2015 [cited 2024 Mar 29 ];2:28-38
Available from: http://www.aaj.eg.net/text.asp?2015/2/1/28/158730


Full Text

 Introduction



Balance in man is a sophisticated and complex mechanism comprised of sensory inputs from the vestibular apparatus, vision, and proprioception. These pass into the central nervous system, are integrated and modulated by the activity of the cerebellum, the extrapyramidal system, the limbic system, and the cerebral cortex, and provide the perception of head and body position in space, eye movement control, and appropriate static and dynamic postural function. Alterations in sensory inputs, integrating mechanisms, or effector organs can result in the perception of dizziness or vertigo, disordered eye movements and disequilibrium, or instability [1] .

Dizziness ranks among the most common complaints in medicine, affecting ~20-30% of the general population. However, the term dizziness encompasses a variety of different sensations, and each points toward a distinct diagnostic direction: rotational vertigo or other illusory sensation of motion indicates vestibular origin, whereas a sensation of light-headedness, giddiness, unsteadiness, drowsiness, or impending faint implies no vestibular origin. Among patients older than 60 years, 20% have experienced dizziness severe enough to affect their daily activities [2] . It is certainly a universal perception among otolaryngologists that dizzy patients represent one of the most frustrating and frustrated groups of patients [3] .

Important causes of vertigo and nonvestibular system disorders have been discussed with focus on benign paroxysmal positional vertigo (BPPV), acute peripheral vestibulopathy, Ménière's disease (MD), toxic damage to the labyrinths, perilymph fistula, cerebrovascular disease, multiple sclerosis, cerebellopontine angle tumors, basilar migraine, vestibular epilepsy, cervical vertigo, and phobic postural vertigo [4] .

Kutz [5] stated that dizzy patients often present a challenge to the physician. The history is the most important component of the evaluation of dizzy patients and often allows the cause of the dizziness to be categorized as peripheral or central. Peripheral causes include BPPV, MD, and vestibular neuritis. Central causes include migraine-associated dizziness, postconcussion syndromes, cerebrovascular disease, and multiple sclerosis. Treatment depends on the cause of the dizziness and may include dietary modifications, diuretics, vestibular suppressants, vestibular rehabilitation, or surgical intervention.

Although dizziness is common and debilitating, clinical diagnosis is often difficult owing to the broad differential diagnosis encompassing vestibular, neurological, and cardiological factors. The physician must rely on a thorough history and physical examination to determine the next steps for evaluation. Once the correct diagnosis is made, effective treatments are often available depending on the cause. However, the burden of diagnosis frequently falls on primary-care and emergency medicine doctors, who face significant time and resource pressures and often find dizziness to be one of the more challenging aspects of practice. Patients' verbal descriptions of the quality of dizziness tend to be unclear, inconsistent, and unreliable, and physicians' dependence on the symptom quality over other clinical features such as the timing and associated symptoms might predispose them to misdiagnosis [6] .

In the face of such diagnostic challenges and in the era of efficiency and cost reduction, a simple, inexpensive, and accurate questionnaire-based diagnostic algorithm would be highly welcome.

Our aim was to develop an Arabic dizziness questionnaire for adults, apply the questionnaire in dizzy patients, and compare the questionnaire conclusion with the results of vestibular evaluation.

 Participants and methods



This study comprised 20 dizzy patients, age 21-60 years, with a mean age of 40.2 ± 11.5 years: participants included 14 women and six men. Normative data of the clinic were used as control data. This study was conducted during the period between July 2012 and December 2013 at the Audiology Clinic, Kasr Al-Ainy Hospital, Faculty of Medicine, Cairo University. The Faculty of Medicine council, Cairo University, ethically approved this study.

All participants underwent the following examinations:

History taking using an Arabic dizziness questionnaire: the adult dizziness questionnaire was designed on a core basis of the pediatric questionnaire [7] and modified by exclusion of the developmental, prenatal, and natal history. Two questions were added under the psychological category: the questions were psychic trauma before the onset of dizziness (Ps1) as it was a risk factor for psychogenic dizziness and hyperventilation associated with the attacks (Ps4) as it is a symptom commonly associated with panic attacks. The questions under general and cardiovascular categories were added together under one category (general) due to overlapping of the questions of both categories. No points were given to Q V5/N5.One point was given to questions related to pressure changes (V8 in the adult questionnaire) instead of 3 points (V9, V10, and V11 in the pediatric questionnaire) as the three questions reflected the same pathology (Appendix).

The adult questionnaire was designed with a total of 18 points for each category: vestibular and neurological categories were given 1 point for each question. The general category was given 1.5 points for each of the 12 questions. The psychological category was given 4.5 points for each of the four questions. The ocular category was given 3 points for each of the six questions. A percentage impairment score was obtained, and the total scoring of each system was calculated. Questionnaire conclusions were built on the results of each category score.Otologic examination including otoscopy and tuning fork tests.Bedside examination of the dizzy patient included search for spontaneous nystagmus, head thrust and head-shake tests, the positioning test, observing the patient's gait, and the Fukuda test.Basic audiological evaluation: Pure tone audiometry: air conduction thresholds were tested at frequencies between 250 and 8000 Hz at octave intervals. Bone conduction thresholds were tested at frequencies between 500 and 4000 Hz, and also at octave intervals with contralateral masking using narrow-band noise effective masking. The degree of hearing loss was calculated on the basis of the pure tone average.Speech audiometry included the speech recognition threshold, using Arabic spondaic words [8] , and the word discrimination score, using Arabic phonetically balanced words [9].Acoustic immittance testing included tympanometry and acoustic reflexes using tone stimuli at 500, 1000, 2000, and 4000 Hz. The frequency of the probe used was 226 Hz.Vestibular evoked myogenic potentials (VEMPs):

First, the skin was cleansed before application of the electrodes to ensure that the impedance is less than 5 kΩ. The active (positive) electrode (first right, then left) was placed on the middle of the sternocleidomastoid muscle, the inverting (negative) on the upper sternum (suprasternal notch), and the ground electrode on the other side. Two repeatable recordings were obtained for each condition. Patients were given 30-60 s to relax between each recording to avoid fatigue. They were asked to flex the neck against resistance.

The stimulus type used was tone burst, of a rarefaction polarity, 1 ms rise/fall time and 2 ms plateau, Blackman ramp, and an intensity of 95 dBnHL presented through TDH39 headphones. The stimulus rate was 5/s. At least 100 sweeps were averaged. The stimulus intensity level of 95 dBnHLwas used as a default starting intensity; two trials were obtained at each intensity to ensure reproducibility. The stimulus intensity was decreased in 10-dB steps or increased in 5-dB steps, depending on the presence or the absence of a VEMP response. The lowest intensity at which a clear and repeatable biphasic wave was observed was considered as the VEMP threshold. The VEMP amplitude (peak to peak) and P13 and N23 latencies were measured at a stimulus level of 95 dBnHL.

VEMP responses were judged as either present or absent according to the presence or the absence of a P13-N23 biphasic response. Parameters analyzed in the preserved VEMP responses were wave latencies, amplitudes, and threshold, P13 and N23 latencies (in 'ms' is the time from the onset of the stimulus to the peak), and the peak-to-peak amplitude (in μV) of the first positive-negative peak (P13-N23).

(6) Computerized dynamic posturography:

All patients were tested by computerized dynamic posturography. The protocol is the sensory organization testing (SOT), which assesses the three sensory components of balance under a variety of altered visual and support surface conditions. Patients were familiarized with the test procedure. Before each section, the patients were given instructions detailing what would follow.

The SOT procedure required individuals to stand on a pressure-sensitive, dynamic-tilted force plate facing a sway referenced visual surround while strapped into a safety harness to prevent injury in the event of a loss of balance [10] . The medial malleolus of each foot was centered directly over the strip on the dual force plate. There were three lateral foot positions, which permitted patients of different heights to have approximately the same degree of difficulty in reaching lateral targets: short (S), medium (M), and tall (T). Proper alignment of the ankle joints with the platform rotation axis gave the most accurate results [11] .

Each test comprises three trials for each of the six conditions representing different aspects of balance. For each condition, an equilibrium score (ES1-6) is calculated that quantifies the center of gravity sway or postural stability under each of the three trials of the six sensory conditions. A score of 100 represents perfect balance (no sway) and a score of 0 represents a potential fall (sway exceeds limits of stability). If at any time during the test, the individual takes a step or requires the assistance of the safety harness, the individual scores a 0 for that test. The average score is calculated for each of the six conditions and a composite equilibrium score is calculated as a weighted average of all six individual scores [10] . Sensory analysis ratios were also used to identify possible impairments of individual sensory systems.

(7) Videonystagmography (VNG):

VNG subtests included oculography tests (smooth pursuit, saccade, and optokinetic), positional tests, positioning tests, and caloric test [11] . The caloric test was performed in the following sequence: left cool, right cool, left warm, and right warm. The irrigation lasted for 40 s. A software algorithm was used to automatically calculate unilateral weakness, directional preponderance, and the total eye velocity using the standard formulae.

Equipment

Sound-treated room, Amplisilence Model E 10070 (Amplisilence s.p.a.,Robassomero, Italy).Two-channel pure-tone audiometer: Grason Staddler (GSI 61; Viasys Healthcare Inc., Eden Prairie, MN, USA), calibrated according to the American National Standards Institute.Immittance meter: Madsen Zodiac 901 middle ear analyzer (GN Otometrics, Taastrup, Denmark), calibrated according to ISO standards. Acoustic reflexes were tested at frequencies of 500-4000 Hz.VEMPs: Biologic, Navigator pro AEP version 6.2.0i00 RevB (Natus Medical Inc., San Carlos, California, USA).Computerized dynamic posturography: Neurocom Smart balance master version 4.01 (Neurocom International Inc., Clackamas, Oregon, USA).Video nystagmography: Micromedical computerized two-channel VNG using monocular goggles (Spectrum software; Micromedical Technologies Inc., Chatham, Illinois, USA).

Statistical analysis

All collected data were revised for completeness and consistency. Precoded data were entered on the computer using the 'Microsoft Office Excel Software' program (2010) for Windows (Microsoft Corporation, Redmond, WA, USA). Data were then transferred to the Statistical Package for Social Science (SPSS) software program, version 21 to be statistically analyzed. Data were summarized using the mean and SD for quantitative variables and the frequency and percentage for qualitative ones. Comparison between groups was performed using the independent-sample t-test for quantitative variables and the χ2 -test or Fisher's exact test for qualitative variables. Pearson correlation coefficients were calculated to signify the association between different quantitative parameters. P-values less than 0.05 were considered statistically significant, and values less than 0.01 were considered highly significant. Graphs were used to illustrate some information.

 Results



The study comprised 20 dizzy patients, their age ranging from 21 to 60 years, with a mean age of 40.2 ± 11.5 years; participants included six men and 14 women.

The predominant diagnoses in the evaluation using the adult dizziness questionnaire were vestibular disorder (15 cases), general disease (one case), combined vestibular and neurologic disorder (one case), combined vestibular and ocular (one case) disorder, combined vestibular general and ocular disorder (one case), and combined vestibular, neurologic, and ocular disorder (one case) ([Figure 1]).{Figure 1}

VNG findings revealed one patient with gaze-evoked nystagmus and abnormal eye movement examination. Five patients had positional nystagmus. Thirteen patients had canal paresis.

Cervical vestibular-evoked myogenic potentials (cVEMPs) were recorded in 18 adult patients on the right side and in 17 patients on the left side. cVEMP was lost bilaterally in two patients; one of them had an unknown cause and the other was diagnosed with arachnoid cyst. cVEMP was lost on the left side in a patient with migrainous vertigo.

The SOT showed a decreased composite score (CS) and vestibular (VEST) ratio in two patients. Three patients showed a decreased CS, VEST ratio, and preference (PREF) ratio. Two patients had a decreased CS, VEST ratio, and visual (VIS) ratio. One patient was diagnosed to have migrainous vertigo and had a low PREF ratio. One patient had low VEST, VIS, and somatosensory (SOM) ratios.

The suggested diagnoses were vestibular neuritis (four cases), MD (four cases), BPPV (three cases), migraine-associated dizziness (three cases), general causes (two cases), cerebellopontine angle (CPA) lesion (two cases), BPPV and unilateral vestibular disorder (one case), and unknown (one case) ([Figure 2]).{Figure 2}

Comparisons and correlations

The vestibular score was compared with canal paresis, and this was not statistically significant ([Table 1]).{Table 1}

cVEMP parameters were compared with the vestibular score, and this was not statistically significant ([Table 2]).{Table 2}

SOT parameters were compared with the vestibular score, and it was nonstatistically significant ([Table 3]).{Table 3}

The questionnaire conclusion in patients diagnosed with vestibular neuritis was the vestibular category. V1 and V7 questions were answered positively by all patients, whereas V18 was answered by three patients.The questionnaire conclusion for MD patients was the vestibular category.V3/N4/G3/Oc1, V17, and V18 questions were answered positively by all patients, whereas V1 was answered positively by three patients.The questionnaire conclusion for BPPV patients was the vestibular category. All patients answered V1, V7, and V15 questions with a 'yes'.In two out of the three migrainous vertigo patients, the questionnaire conclusion was vestibular category. All patients had within-normal hearing sensitivities. V3/N4/G3/Oc1 and N5 questions were answered with a 'yes' by all patients. One patient also answered V7, N8, N11, N12 questions positively. This patient had an interaural amplitude difference (IAD) of 0.35 in cVEMP response and had a vestibular deficit in SOT.

 Discussion



Dizziness is among the most common complaints leading to a visit to a physician for all age groups [12] . Medical history taking alone reveals the diagnosis in roughly three out of four patients complaining of dizziness [13] . The use of a screening questionnaire to evaluate dizzy patients guides the direction of the diagnostic work-up. The majority will be sorted into correct diagnostic groups before the physical examination and diagnostic work-up are undertaken. The extended work-up can then be tailored to answer more specific questions rather than using the same shotgun approach on every dizzy patient [3] .

This study included 20 dizzy patients, their age ranging from 21 to 60 years, with a mean age of 40.2 ± 11.5 years. Thirty percent of the patients were male and 70% were female. This was in agreement with Neuhauser et al. [14] , who reported a marked female preponderance among individuals with dizziness (1-year prevalence ratio male to female 1 : 2.7). This was also in agreement with Agus et al. [15] , who reported that the majority of the patients were female (65.3%) and over 65% were between the age of 41 and 70 years, with a mean age at diagnosis of 56.1 years.

In this research, the predominant diagnoses of the evaluation of patients using the adult dizziness questionnaire were vestibular disorder (15 cases), general disease (one case), combined vestibular and neurologic disorder (one case), combined vestibular and ocular disorder (one case), combined vestibular, general, and ocular disorder (one case), and combined vestibular, neurologic, and ocular disorder (one case) ([Figure 1]). This was in contrast to Neuhauser et al. [14] , who reported that vestibular vertigo accounted for almost a quarter (24%) of the dizziness/vertigo cases in the community. However, this finding could be attributed to the conductance of our study in an audiology clinic.

The suggested diagnoses in this study were vestibular neuritis (four cases), MD (four cases), BPPV (three cases), migraine-associated dizziness (three cases), general causes (two cases), CPA lesion (two cases), BPPV and unilateral vestibular disorder (one case), and unknown (one case) ([Figure 2]). This is in agreement with Zhao et al. [6] , who reported that the four most common diagnoses were BPPV (164 individuals; 26.5%), migraine dizziness (101 individuals; 16.3%), MD (82 individuals; 13.2%), and vestibular neuritis (49 individuals; 7.9%). Together, these four diagnoses made up 64% of the total number of their patients.

Agus et al. [15] collected data from 4294 patients with vertigo in 13 countries. He reported that the most common diagnoses of vertigo were BPPV (26.9%), peripheral vestibular vertigo of unknown origin (20.5%), MD (15.4%), and 'other vertigo of peripheral vestibular origin' (37.2%).

Kentala and Rauch [3] evaluated 57 patients (42 women and 15 men) for dizziness. Thirty-five (61.4%) of the 57 individuals belonged to the four common disease groups: BPPV, MD, labyrinthitis, and vestibular neuritis. Of the remaining 22 individuals, eight (14%) had migraine-associated dizziness, whereas the other 14 had a variety of other peripheral, central, or undiagnosed abnormalities.

The vestibular score of the dizziness questionnaire was compared with canal paresis, cVEMPs parameters, and SOT parameters, and these were not statistically significant ([Table 1], [Table 2] and [Table 3]). These findings could be attributed to the variability of the findings of vestibular assessment in each disorder, and variability even in the findings of patients sharing the same diagnosis.

The most valuable questions in the diagnosis of vestibular neuritis were 'whirling nature of the attack' (V1) and 'precipitation of the attack by head movement' (V7). There was a history of viral infection before the first attack in 75% of the patients. The first attack was severe and prolonged for hours with severe deterioration of balance. Kentala and Rauch [3] reported that dizziness due to vestibular neuritis is persistent vertigo without hearing loss. Zhao et al. [6] reported that vestibular neuritis was positively predicted by nausea and nasal obstruction. The predictive power for vestibular neuritis was less than expected as some patients had two types of dizziness, such as comorbid BPPV and vestibular neuritis.

In this study, the most valuable questions in diagnosing MD were a sensation of unsteadiness and a sense of falling (V3/N4/G3/Oc1), associated auditory symptoms that may appear before the attacks (V17), and auditory complaints (V18). Zhao et al. [6] reported that MD was positively predicted with auditory changes during the attack such as hearing changes, a sensation of the world spinning, male sex, and unilateral tinnitus. Kentala and Rauch [3] reported that dizziness due to MD is persistent vertigo with hearing loss. Bayer et al. [16] reported that the diagnosis of MD was predicted by vertigo appearing in attacks, the perception of the environment, and concomitant symptoms such as tinnitus, nausea, sweating, and vomiting.

The most valuable questions in diagnosing BPPV were the whirling nature of the attacks (V1), precipitation of the attacks by head movements (V7), and relief from the attack by keeping the head still (V15). The attacks were very short and associated with nausea. BPPV was positively predicted with a history of dizziness when lying down, dizziness with head movement, and dizziness when bending over. Patients were free from dizziness between attacks. Incidence of BPPV increases with age increases the possibility of diagnosis (age range 19-89 years), and attacks about seconds [6] .

In this study, the most valuable questions in diagnosing migrainous vertigo were a sensation of unsteadiness and a sense of falling [V3/N4/G3/Oc1 and Aura before the attacks (N5)]. Kentala and Rauch [3] reported that in patients with migraine-associated dizziness, the sense of dizziness was most often disequilibrium or moderate-duration episodes of true vertigo, without hearing loss. Migraine dizziness was most positively correlated with light sensitivity, menstrual cycles, and severe or recurrent headaches [6] .

Vestibular assessment was abnormal in 17 patients, whereas only 15 patients were suggested to be of the vestibular category by the questionnaire. The questionnaire missed two cases whose diagnoses were CPA lesions and one patient with migrainous vertigo. One patient was suggested to have a vestibular category using the questionnaire, but results of vestibular assessment were within normal. This patient was diagnosed with migrainous vertigo (MV).

 Conclusion



Although comparisons and correlations between the vestibular score of the dizziness questionnaires and the results of the different tests used in vestibular assessments were nonstatistically significant, patients sharing the same diagnosis consistently answered certain questions positively. In this study, the most common causes of dizziness in the adult group were vestibular neuritis (four patients out of 20), MD (4/20), BPPV (3/20), and migrainous vertigo (3/20).

We recommend the use of the dizziness questionnaire as a first step in the evaluation of dizzy patients. However, the use of the dizziness questionnaires to evaluate dizzy patients is not a substitute for a neuro-otologic evaluation. We recommend a complete battery of assessment that includes careful history taking, a detailed otologic and neurologic physical examination, and appropriate diagnostic tests and procedures.

 Acknowledgements



Conflicts of interest

None declared.

References

1Luxon LM. Evaluation and management of the dizzy patient. J Neurol Neurosurg Psychiatry 2004; 75 :45-52.
2Chu Y, Cheng L. Vertigo and dizziness. Acta Neurol Taiwan 2007; 16 : 50-60.
3Kentala E, Rauch SD. A practical assessment algorithm for diagnosis of dizziness. Otolaryngol Head Neck Surg 2003; 128 :54-59.
4Mukherjee A, Chatterjee SK, Chakravarty A. Vertigo and dizziness - a clinical approach. J Assoc Physicians India 2003; 51 : 1095-1099.
5Kutz J. The dizzy patient. Med Clin North Am 2010; 94 :989-1002.
6Zhao J , Piccirillo J , SpitznagelJr E , Kallogjeri D, Goebel J. Predictive capability of historical data for diagnosis of dizziness. Otol Neurotol 2011; 32 :284-290.
7Shabana M, Dabbous A, Hosni N, Medhat M. Can scoring of symptoms in dizzy children aid the categorization of causes of dizziness for accurate referral? Egypt J Otolaryngol 2012; 28 :214-233.
8Soliman S, FathAllah A, Shehata W. Development of the Arabic staggered spondiac word (SSW) test. In the 8th Annual Ain Shams Medical Congress; Cairo, Egypt; March 1-5 1985. pp. 1229-1245.
9Soliman S. Speech discrimination audiometry using Arabic phonetically balanced words. Ain Shams Med J 1976; 27 :27-30.
10Zammit G, Wang-Weigand S, Peng X. Use of computerized dynamic posturography to assess balance in older adults after night time awakenings using zolpidem as a reference. BMC Geriatr 2008; 8 :15-21.
11Farid AS, Shabana M, El khousht M, El fouly H, Hamdi M. Difficulties encountered during vestibular testing of pediatric patients (aged 6-12 years). Med J Cairo Univ 2012; 80 :17-24.
12Karatas M. Central vertigo and dizziness: epidemiology, differential diagnosis, and common causes. Neurologist 2008; 14 :355-364.
13Labuguen R. Initial evaluation of vertigo. Am Fam Physician 2006; 73 :244-251.
14Neuhauser H, Von Brevern M, Radtk A, Lezius F, Feldmann M, Ziese T, Lempert T. Epidemiology of vestibular vertigo: a neurotologic survey of the general population. Neurology 2005; 65 :898-904.
15Agus S, Benecke H, Thum C, Strupp M. Clinical and demographic features of vertigo: findings from the REVERT registry. Front Neurol 2013; 4 :1-8.
16Bayer O, Warninghoff J, Straube A. Diagnostic indices for vertiginous diseases. BMC Neurol 2010; 10 :98-104.