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Keywords:

  • intracranial arachnoid cysts;
  • dizziness;
  • postural balance;
  • vertigo

Abstract

  1. Top of page
  2. Abstract
  3. Introduction
  4. Patients and methods
  5. Results
  6. Discussion
  7. Conclusion
  8. Authors’ contributions
  9. Acknowledgement
  10. Funding
  11. Conflict of interest
  12. Ethical approval
  13. References

Objectives

Arachnoid cysts (AC) are benign, congenital malformations of the leptomeninges, with a predilection for the temporal fossa. In our clinical experience, patients with temporal AC often complain of dizziness and imbalance. However, these symptoms and the effect of surgery on them have not been studied before.

Materials and methods

Dizziness and imbalance in patients with temporal AC were quantified before and after surgical cyst decompression, using the Dizziness Handicap Inventory (DHI), Vertigo Symptom Scale – Short-Form (VSS-SF) and computerized dynamic posturography (CDP). The study includes 16 patients with temporal AC and 15 control subjects undergoing surgery for benign lesions of the larynx (n = 10) or the parotid glands (n = 5). All participants answered the DHI and VSS-SF and underwent CDP the day before and 3–6 months after surgery. The patients with AC also graded their dizziness through the use of a visual analogue scale (VAS).

Results

Preoperatively, cyst patients scored higher than controls on subjective symptoms (DHI, VSS-SF A and VSS-SF V), but not on postural sway (CDP). Symptom scores decreased after surgery; the cyst patients improved significantly in the subjective tests (DHI, VAS and VSS-SF), while CDP scores did not. In the controls, symptom and CDP scores were unchanged after surgery.

Conclusions

Patients with temporal AC have a significant preoperative impairment and post-operative improvement in their subjective dizziness, but not in postural sway as measured by CDP.


Introduction

  1. Top of page
  2. Abstract
  3. Introduction
  4. Patients and methods
  5. Results
  6. Discussion
  7. Conclusion
  8. Authors’ contributions
  9. Acknowledgement
  10. Funding
  11. Conflict of interest
  12. Ethical approval
  13. References

Arachnoid cysts (ACs) are benign, congenital malformations of the leptomeninges. These cysts have a predilection for the temporal fossa, more commonly on the left side and in males, but they may also be found in the posterior or anterior fossae [1].

Most arachnoid cysts are expansive and can be seen to compress nearby brain tissue or cerebrospinal fluid (CSF) compartments. The patient may be asymptomatic or may experience a variety of symptoms, most commonly headache, and surgical cyst decompression may decrease or eliminate these symptoms, as shown both in children and adults [2, 3]. ACs have also been demonstrated to yield dyscognition, which normalizes after surgical cyst decompression [4].

Symptoms of disequilibrium, including dizziness, vertigo and imbalance, have also been related to arachnoid cysts, not only those occupying the posterior fossa; dizziness and vertigo are in fact common subjective complaints in patients with temporal cysts [5].

Although these symptoms have a major negative impact on health-related quality of life in patients with vestibular disorders [6, 7], they have not been studied systematically in patients with arachnoid cysts. Moreover, no one has investigated whether the subjective dizziness in these patients is associated with objective signs of impaired balance.

The aims of this study were to find out whether patients with temporal AC experience more dizziness than the normal population, to characterize their dizziness using the Dizziness Handicap Inventory (DHI), Vertigo Symptom Scale – Short-Form (VSS-SF) and dynamic computerized posturography (CDP), and finally, to investigate whether surgical cyst decompression improves dizziness or postural imbalance. As our previous studies have been based solely on the patients’ own reports on dizziness combined with visual analogue scale scores, we wanted to use questionnaires specially designed to probe vertigo and dizziness to obtain more reliable information on this topic.

Patients and methods

  1. Top of page
  2. Abstract
  3. Introduction
  4. Patients and methods
  5. Results
  6. Discussion
  7. Conclusion
  8. Authors’ contributions
  9. Acknowledgement
  10. Funding
  11. Conflict of interest
  12. Ethical approval
  13. References

Patients

The study included 16 consecutive patients (11 males, 5 females; mean age 44; median age 43; range 15–74) with a total of 17 symptomatic arachnoid cysts (one patient with bitemporal cysts) in the temporal fossa, who were referred to and operated for these cysts in the Department of Neurosurgery, Haukeland University Hospital. All the patients were referred for symptoms assumed to be caused by the cyst, with headache as the most prominent symptom followed by vertigo/dizziness, and therefore offered surgical cyst decompression.

According to the Galassi classification [8], eleven of the cysts were of type I, four were of type II and two cysts were larger than that (types II–III).

Controls

The control group consisted of 15 patients (7 females and 8 males) with a mean age of 49 years (range 28–66) undergoing surgery for benign lesions of the larynx (n = 10) or the parotid gland (n= = 5). The controls were included to control for preoperative nervousness/anxiety before surgery or a post-operative relief/learning effect of the test as possible causes of any observed preoperative impairment or post-operative improvement in the cyst patients, respectively.

Methods

Test procedures

The cyst patients and the controls were tested on two occasions. The first test was performed one day before surgery and the second test for the cyst patients between 3 and 6 months after cyst surgery. The time span between the pre- and post-operative tests for the controls was at least 4 weeks.

The cyst patients were asked to grade their symptoms of vertigo and dizziness on a visual analogue scale (VAS). In addition, both cyst patients and controls answered the Dizziness Handicap Inventory (DHI) and the Vertigo Symptom Scale – Short-Form (VSS-SF), and their balance was tested by computerized dynamic posturography (CDP) using the Sensory Organization Test (SOT) protocol.

Four cyst patients had more than one post-operative test as they had a minor complication that is relatively common after cyst decompressions (chronic subdural hygroma/haematoma). In these patients, we used the results from the preoperative testing, and the final testing after the post-operative complication had been successfully dealt with. One of these patients gave post-operative answers to the questionnaires twice, but had only one post-operative test on the balance platform (SOT). The post-operative SOT result of this patient was included in the study, although he had a non-symptomatic chronic subdural haematoma (CSDH) at the time. We chose to do so because he had normal scores on both the subjective and the objective (SOT) tests, and the test results thus did not seem to be greatly affected by his post-operative CSDH. The patient with bilateral cysts was also tested more than once, because he was operated twice, first on one side and then on the other. For this patient, the preoperative test results and the final post-operative test results after the second cyst operation were used.

Surgery

The patients were operated with a craniotomy in general anaesthesia. During this operation, the parietal cyst membrane was removed, and the medial remaining membrane, covering the basal structures (the tentorial slit, the oculomotor nerve, the carotid artery and the optic nerve) was fenestrated, thus creating communication to the basal cisterns and the posterior fossa. When accessible, the arachnoid covering the sylvian fissure was also opened, thus creating communication to the subarachnoid space surrounding the carotid and the middle cerebral arteries. The details of the procedure have been published previously [2].

Scoring of clinical and neuroimaging results

The clinical and neuroimaging results were scored according to the outcome classification that our group has used previously [2, 3].

Clinical results

The patients with ACs were categorized into one of four clinical outcome groups (COGs) based on a questionnaire including a VAS score and information from pre- and post-operative medical records. For patients in COG 1, the preoperative symptoms had disappeared. For COG 2, the symptoms were reduced, but still present. For COG 3, the symptoms were unchanged, and in COG 4, the patient had more post-operative complaints than before the operation.

Neuroimaging results

Neuroimaging results were defined as change in cyst volume on the post-operative neuroimaging examination 3–6 months after cyst decompression. The radiological results were categorized into one of four possible neuroimaging outcome groups - NOGs. In NOG 1, the cyst was no longer visible. In NOG 2, a fluid volume was still visible, smaller than 50% of the preoperative cyst volume. In NOG 3, the post-operative fluid volume was reduced, but it was larger than 50% of the preoperative cyst volume; in NOG 4, there was no change in the volume.

A successful decompression was defined as a clear-cut radiological and/or clinical improvement. According to these criteria, all cysts were successfully decompressed. Four patients had post-operative complications (chronic subdural hygromas/haematomas) that required a minor surgical procedure (burr hole and irrigation/evacuation in local anaesthesia). In these patients, the post-operative testing was performed after the patients were fully recovered, from 7 to 16 months after the primary operation, as mentioned above.

Test apparatus – computerized dynamic posturography

Postural sway was measured using a commercially available force platform (EquiTest®, Neurocom, USA) and the Sensory Organization Test (SOT) protocol, which has been described elsewhere [9]. None of the cyst patients or controls had medical conditions or medication that eliminated them from being tested by the Sensory Organization Test (SOT) [10].

The test is non-invasive and causes no discomfort. The SOT measures postural sway under six different conditions. Each condition conflicts or removes one or more of the balance mechanism components (vision, proprioception or equilibrium). An equilibrium score from 0 to 100 is calculated for each condition where 100 represents an immobile patient and 0 represents a fall. A composite score (COMP) is calculated as the weighted average of the six equilibrium scores [11].

The conditions are as follows:

1st condition (SOT1): visual surround is stable (eyes open), and the platform is stable.

2nd condition (SOT2): visual surround is stable (eyes closed), and the platform is stable.

3rd condition (SOT3): visual surround moves (eyes open), and the platform is stable.

4th condition (SOT4): visual surround is stable (eyes open), and the platform moves.

5th condition (SOT5): visual surround is stable (eyes closed), and the platform moves.

6th condition (SOT6): visual surround moves (eyes open), and the platform moves.

The composite score (COMP) of the SOT was used to compare the results between the groups before and after surgery. The normative values for the COMP are given in three age groups: 20–59 years: COMP = 79.787; 60–69 years: COMP = 77.589; and 70–79 years: COMP = 72,850 [10]. Three cyst patients were under the age of 20 at the time of the first test. These three are compared with the normative COMP as if they were 20 years of age, as we assume that the expected balance function is the same for the age group 16–19 as for those who are 20 years.

Possible learning effect

Healthy people are able to improve their SOT scores when retested within 3 months (12). The mean equilibrium scores for conditions 1–3 reflect no significant learning effect when subjects are retested [12, 13]. For conditions 4 through 6, however, one must use a criterion of 8-point improvement in the composite score of the SOT to indicate improvement beyond the learning effect, according to Wrisley et al. [12].

Dizziness Handicap Inventory

The effect of dizziness on everyday life was measured using a translated (Norwegian) and validated version of the Dizziness Handicap Inventory [14]. The DHI is a 25-item questionnaire that quantifies the handicapping effect of dizziness on everyday life. The response categories are ‘yes’, ‘sometimes’ or ‘no’ to each question, giving 4, 2 or 0 points, respectively. This gives a summary score ranging from 0 to 100, with higher scores indicating a greater handicap. A score of ≤30 indicates a mild handicap, a score from 31–60 indicates a moderate handicap, and a score of >60 indicates a severe handicap [15]. Patients who score more than 60 on the DHI are regarded as functionally impaired [15].

Vertigo Symptom Scale – Short-Form

A translated (Norwegian) and validated version [16] of The Vertigo Symptom Scale – Short-Form (VSS-SF) [17, 18] was used in this study. This questionnaire consists of 15 items and captures the severity of vertigo symptoms during the last month. It measures frequency of dizziness, vertigo, imbalance and related autonomic symptoms.

Response categories are ‘never’, ‘some times’, ‘several times’, ‘frequently’ or ‘often (almost daily)’, giving points of 0, 1, 2, 3 or 4, respectively. A summary score is calculated yielding a score range from 0 to 60 VSS-SF points, and severe dizziness is indicated by a score of ≥12 VSS-SF points, and a change of 3 points on the total scale has been suggested as reflecting a true change [19]. Two subscales exist, vertigo–balance (VSS-SF V, 8 items, score range 0–32 VSS-SF points) and autonomic anxiety (VSS-SF A 7 items, score range 0–28 VSS-SF points); these two subscales relate to whether the complaints/symptoms are caused by balance-associated problems or anxiety. The following cut-off values have been established and were used for the controls and cyst patients in our study: 6.5 for VSS-SF, 2.5 for VSS-SF V (vertigo) and 3.5 for VSS-SF A (anxiety) [16]. Accordingly, a score of ≤6.5 indicates no problem with dizziness and vertigo, a score between 6.6 and 12 indicates a moderate problem, and scores above 12 indicates a severe problem.

Visual Analogue Scale

The visual analogue scale (VAS) was used to indicate how the patients experienced the effect of dizziness and vertigo on an everyday basis. The VAS is a 10-cm scale anchored at each side by extreme statements. A score of zero indicates no symptoms of dizziness or vertigo in everyday life, and a score of 10 indicates that the subject defines his/her symptoms as the worst thinkable. The VAS has been shown to be effective in measuring symptoms of dizziness and vertigo [20-22].

Statistics

Statistical analyses were performed using IMB SPSS Statistics version 18.0. Mean, median and standard deviation were used to describe the two groups pre- and post-operatively with respect to VAS dizziness score (cyst patients only), VSS-SF total and subscales, the DHI total score and the SOT total score.

Patients and controls were compared using the Mann–Whitney two-sample rank-sum test. Pre- and post-operative test results for VSS-SF total and subscales, the DHI total score and the SOT composite score were compared for patients and controls using Wilcoxon signed ranks test. Statistical significance was set at P ≤ 0.05 (two-tailed).

Results

  1. Top of page
  2. Abstract
  3. Introduction
  4. Patients and methods
  5. Results
  6. Discussion
  7. Conclusion
  8. Authors’ contributions
  9. Acknowledgement
  10. Funding
  11. Conflict of interest
  12. Ethical approval
  13. References

Clinical and neuroimaging results

Table 1 gives an overview of the patient characteristics, clinical and neuroimaging results and the pre- and post-operative results of the disequilibrium tests. All the patients exhibited either a clinical or a radiological improvement or both.

Table 1. Individual data for all the 16 cyst patients. For NOG, COG and test names, see text
Pat. no.AgeGenderSympt.TypeSideNOGCOGPreoperative testsPost-operative tests
VASVSSDHISOTVASVSSDHISOT
  1. Abbreviations for symptoms: D: dyscognition; E: epilepsy; H: headache; V: vertigo.

  2. VAS, Visual analogue scale; DHI, Dizziness Handicap Inventory; VSS-SF, Vertigo Symptom Scale – Short-Form; VSS-V, Vertigo Symptom Scale – vertigo; VSS-A, Vertigo Symptom Scale – anxiety; NOG, neuroimaging outcome groups; COG, clinical outcome groups; SOT, Sensory Organization Test.

116MHIL1174780083
241MHIL329114063333079
339MD+HIL4146831.572084
456MD+HIIR212.592464132061
515FHIIL2231322750.55284
631FHIL225.571687131488
756ME+HI+IL/R4 + 4121288404477
838MHIIL223.51840770121085
964MD+EII-IIIL211307700078
1027FD+HIR4161248830152683
1162MD+HIIR2111107700084
1246FE+HII-IIIR211854433.5154052
1344FH+D+VIL3252855563453
1450ME+HIL41508401081
1543MHIR117128602683
1674MH+VIR2161250745272
Clinical results

All cyst patients experienced post-operative subjective improvement. According to the classification of clinical results used by Helland and Wester [2, 3], the final results were as follows: 11 patients had no longer any complaints (COG 1) and 6 patients were improved, but still had some remaining complaints (COG 2). Four patients had a post-operative CSDH that was successfully drained by a minor surgical procedure (burr hole in local anaesthesia). The COG classification and the test results used in the analyses are the final COG scores obtained after this evacuation.

There was no correlation between the degree of clinical improvement and gender, age, sidedness of cyst or cyst size according to the Galassi classification [8].

Neuroimaging results

A reduction in the fluid volume where the cyst had been located could be seen in a total of 12 of the 17 cysts. According to the classification of neuroimaging outcome used by Helland and Wester, the details of the neuroimaging results were as follows: NOG 1 (cyst no longer visible): 2 cysts; NOG 2 (reduced to below 50% of original volume): 8 cysts; NOG 3 (reduced, but above 50% of original volume): 2 cysts; and NOG 4 (no visible change): 5 cysts.

Preoperative symptom scores and posturography

The cyst patients scored higher than the controls on all symptom scales, but the posturography results were similar (SOT – Tables 1, 2).

Table 2. Preoperative descriptive data from all the tests for patients and controls and P-values from Mann–Whitney U-test comparing cyst patients and controls. The reason the SOT normative data (‘Norm’) different for the cyst patients and the controls is the slightly different age composition of the two groups. = normative data. Only 11 cyst patients were tested with VAS preoperatively
TestCyst patients’ score (n = 16)Controls score (n = 15)Mann–Whitney U-scoreP-value
VAS
Mean3.68 
Median3.00  
St. Dev.2.62  
VSS-SF
Mean10.632.0013.0<0.001
Median10.001.00  
St. Dev.6.222.33  
VSS-A
Mean7.131.8027.0<0.001
Median6.501.00  
St. Dev.4.002.01  
VSS-V
Mean3.500.2037.5<0.001
Median3.000.00  
St. Dev.3.350.41  
DHI
Mean20.130.0022.5<0.001
Median15.000.00  
St. Dev.18.310.00  
SOT
Mean74.3877.47123.50.382
Median77.0076.00  
St. Dev.12.276.05  
Norm79.0879.49  
Symptom scores

The cyst patients scored higher than the controls on the VSS-SF and the DHI (Tables 1, 2). The scores indicated a moderate preoperative dizziness in the cyst patients, but not in the controls. This also applied to the two subscales of the VSS-SF. The results of the controls in the VSS-SF, including the subscales VSS-V and VSS-A, and DHI indicated no dizziness problems.

Based on the individual scores (Table 1), six patients had preoperative VSS scores that indicated a severe dizziness handicap (≥12); four of them also had DHI scores in the range 31–60, indicating a moderate handicap.

VAS

Due to logistical problems, we obtained a pre- and post-operative VAS score for only 9 cyst patients with a mean score of 3.68 preoperatively (Tables 1, 2). The controls were not asked to fill in the VAS.

Posturography

The cyst patients did not differ significantly from the controls or from normative data with respect to SOT composite scores (Tables 1, 2). Four patients had clearly subnormal scores in the SOT test (Table 1); only one of them (pat. no. 12) had also scores on both VSS and DHI that indicated severe and moderate dizziness, respectively. The other three patients also had high scores on one or both of the subjective tests, but not as severe. None of the controls had subnormal scores in the SOT test.

Post-operative tests

Symptom scores

In general, the cyst patients improved significantly in symptom scores after surgical cyst decompression on all the subtests (Table 3). Preoperatively, the controls had normal scores on the post-operative VSS-SF and DHI, and they did not improve post-operatively (Table 4).

Table 3. Cyst patients preoperatively vs post-operatively
TestDifference of mediansP-value
  1. Difference of medians and P-values from Wilcoxon rank-sum tests comparing preoperative and post-operative performance of the cyst patients in subjective and objective tests. All differences are in the direction of an improved performance.

VAS2.090.007
VSS-SF6.190.004
VSS-A4.060.014
VSS-V2.130.003
DHI7.630.05
SOT−2.000.155
Table 4. Post-operative descriptive data from all the tests for patients and controls and P-values from Mann–Whitney U-test comparing cyst patients and controls. The reason the SOT normative data (‘Norm’) different for the cyst patients and the controls is the slightly different age composition of the two groups
TestCyst patients’ score (n = 16)Controls score (n = 15)Mann–Whitney U-scoreP-value
VAS
Mean1.72 
Median0.75  
St. Dev.2.36  
VSS
Mean4.441.7381.50.021
Median3.501.00  
St. Dev.4.722.19  
VSS-A
Mean3.061.3388.00.039
Median2.500.00  
St. Dev.3.471.88  
VSS-V
Mean1.380.4089.00.043
Median1.000.00  
St. Dev.1.670.74  
DHI
Mean12.500.2743.5<0.001
Median5.000.00  
St. Dev.14.131.03  
SOT
Mean76.3879.87106.50.149
Median81.0082.00  
St. Dev.11.617.56  
Norm79.0879.49  
Cyst patients vs controls

A comparison between the patients and the controls shows that even if the cyst patients had improved post-operatively, they still had more subjective symptoms and handicap from dizziness and vertigo than the controls after surgery (Table 4).

Posturography

Preoperatively, the cyst patients had a slightly lower post-operative score on the SOT than the controls, but the difference was not significant. Neither patients nor controls differed significantly from the normative data (Table 4).

Discussion

  1. Top of page
  2. Abstract
  3. Introduction
  4. Patients and methods
  5. Results
  6. Discussion
  7. Conclusion
  8. Authors’ contributions
  9. Acknowledgement
  10. Funding
  11. Conflict of interest
  12. Ethical approval
  13. References

The data presented here indicate that patients with temporal arachnoid cysts are handicapped by vertigo and dizziness in their everyday life. As a group, they had significantly higher preoperative symptom scores (DHI, VSS-SF A and VSS-SF V) than the controls and also higher than previously found in healthy persons in several populations [23-25].

However, it is of some interest to note that for the cyst patient group as a whole, this subjective dizziness was not paralleled by any demonstrable postural instability, neither when compared with the controls nor to normative data. Such a discrepancy between subjective dizziness and objective postural instability is, however, not so uncommon [26]. A possible explanation is that patients often experience dizziness and vertigo in attacks or over brief periods. Often the symptoms are caused by head motions or particular visual stimuli. It is therefore conceivable that postural stability could be normal between attacks and during dynamic posturography when the head is kept still and visual field motion is minimal. The perception of dizziness and vertigo is thought to arise from a sensory mismatch in the cortex of the brain between vestibular and visual stimuli, while postural instability may result from a wide variety of vestibular, neurological and orthopaedic disorders. A vestibular area has been identified in the temporal cortex, which could be linked to the perception of self-motion, but this area is also influenced by optokinetic stimuli from the visual system, which explains why it is difficult in many situations to distinguish between self-motion and visual field motion [27, 28].

We suggest that a pressure effect of temporal arachnoid cysts on the vestibular cortex could explain why they cause dizziness and vertigo, without necessarily disturbing standing steadiness, which to a greater extent is maintained by the cerebellum and the brainstem.

Although the cyst patients as a group did not exhibit impaired performance on the balance platform, some of the individuals in that group (pats. no. 2, 4, 12, and 13, see Table 1) had scores on the SOT test that definitely was below normal, and they also had relatively high scores in the subjective VSS and/or DHI tests. It is thus possible that the cortical modulation of the basic equilibrium mechanisms of the cerebellum and the brainstem can be strong enough to not only give a subjective impression of dizziness, but also to influence the performance on the balance platform in some cyst patients.

We included other patients scheduled for ENT surgery as controls, not only for comparison purposes in the preoperative tests, but also to be able to control for a general learning effect as well as preoperative anxiety and post-operative relief as possible causes of any preoperative impairment or post-operative improvement, respectively. Our results indicate that such contaminating factors most likely can be ruled out as causes of preoperative impairment or post-operative improvement, unless the preoperative anxiety was larger in the cyst patients than in the ENT patients. This, however, cannot entirely be ruled out; the surgical ENT procedures for the controls may have been perceived as more trivial than the upcoming intracranial procedure that was perceived by the cyst patient. Unless one uses other patients scheduled for intracranial surgery as control, which inevitably would involve patients with more severe intracranial conditions that would affect cognition and probably also steadiness, our controls were probably the best controls available, as they all were scheduled for surgery as close to the neurocranium as possible. Other known causes of impaired SOT performance [29-32] were not present in our cyst patients.

We believe that the differences in age and gender between the cyst patients and the controls are of little importance when it comes to post-operative improvement, as all the participants were tested against themselves, and the SOT is programmed to compare the results of the test with age-specific normative data [33].

Our study shows that the cyst patients’ scores in all the subjective tests improved significantly after the cyst decompression, indicating that they were less affected by dizziness and vertigo in their everyday lives after the operation. That this subjective improvement was not paralleled by an improved performance in the objective balance test is only to be expected, as the cyst patients as a group had a normal preoperative performance in the SOT test.

Conclusion

  1. Top of page
  2. Abstract
  3. Introduction
  4. Patients and methods
  5. Results
  6. Discussion
  7. Conclusion
  8. Authors’ contributions
  9. Acknowledgement
  10. Funding
  11. Conflict of interest
  12. Ethical approval
  13. References

Our study shows that patients with temporal arachnoid cysts experience and are handicapped in their everyday life by subjective symptoms of dizziness and vertigo. Surgical decompression of the cysts gives a significant improvement of these subjective complaints. These changes in subjective symptoms, however, were not related to any demonstrable changes in postural sway during dynamic posturography.

Authors’ contributions

  1. Top of page
  2. Abstract
  3. Introduction
  4. Patients and methods
  5. Results
  6. Discussion
  7. Conclusion
  8. Authors’ contributions
  9. Acknowledgement
  10. Funding
  11. Conflict of interest
  12. Ethical approval
  13. References

IF and CT participated equally in the testing of the patients, the analyses of the test results and in the preparation of the manuscript. CAH and KGW participated in designing the study, operated all the patients, analysed the clinical and neuroimaging results and the correlation between those and the test results and participated in the final preparation of the manuscript. KW and FG participated in designing the study and the preparation of the manuscript. They also participated in and supervised the testing.

Funding

  1. Top of page
  2. Abstract
  3. Introduction
  4. Patients and methods
  5. Results
  6. Discussion
  7. Conclusion
  8. Authors’ contributions
  9. Acknowledgement
  10. Funding
  11. Conflict of interest
  12. Ethical approval
  13. References

This work was supported by two research grants to Christian A Helland from Health Region West, Norway, Grant Numbers: 911065 and 911475.

Ethical approval

  1. Top of page
  2. Abstract
  3. Introduction
  4. Patients and methods
  5. Results
  6. Discussion
  7. Conclusion
  8. Authors’ contributions
  9. Acknowledgement
  10. Funding
  11. Conflict of interest
  12. Ethical approval
  13. References

Ethical approval for the present study was obtained from the regional ethics committee – Health Region West (Regional komité for medisinsk og helsefaglig forskningsetikk, Vest-Norge (REK Vest)), postal address: REK Vest, University of Bergen, Medical Faculty, mailbox 7804, N-5020 Bergen, Norway, and the study has therefore been performed in accordance with the ethical standards laid down in the 1964 Declaration of Helsinki and its later amendments.

References

  1. Top of page
  2. Abstract
  3. Introduction
  4. Patients and methods
  5. Results
  6. Discussion
  7. Conclusion
  8. Authors’ contributions
  9. Acknowledgement
  10. Funding
  11. Conflict of interest
  12. Ethical approval
  13. References
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