The study was conducted as an extension of the Erfurt Neurofibromatosis Database Research (NF registry), which contains disease data on patients diagnosed with NF2-SWN. This database is an online registry of the Castor EDC platform that complies with European data protection laws. The registry is approved by the regional ethics board and collects patient data under a pseudonym. It is updated regularly at each hospital or outpatient visit. The investigation was approved by the local ethics committee of Erfurt (ref:2278/2020/6). All patients gave written informed consent. STROBE guidelines for cross-sectional studies were used13. The study was conducted in accordance with the Declaration of Helsinki.
An open web-based survey was conducted from December 2021 to January 2022 using the SoSci Survey online tool. n= 97 patients at the Neurofibromatosis Center in Erfurt were invited by e-mail to volunteer for an online survey. The survey included questions about age, gender and date of birth. The date of birth from the survey data had to match the data from the NF register. Inclusion criteria were the diagnosis of “NF2-related schwannomatosis” and a minimum age of 16 years.
Disease severity
The clinician-reported disease severity score consisted of 7 symptoms with a major impact on the patient’s life: (1) hearing loss in both ears; (2) severe visual impairment in both eyes; (3) bilateral facial paralysis, at least on one side ≥ H&B°3; (4) depression/anxiety disorder; (5) severe chronic pain/substance abuse due to pain; 6) immobility; and (7) malignancies9. In the absence of all points, the severity is assessed as mild, 1-3 symptoms are indicated as moderate severity and 4-7 symptoms are reported in case of severe NF2-SWN. The disease severity score ranges from 1 (= mild) to 3 (= severe). Disease severity of participants was assessed based on data from the NF registry. The disease severity score was derived from the most recent clinical data available in the NF registry. This result has been validated (publication currently under review) and a version of it is described in detail in a recent publication9.
Health-related quality of life
Hornigold et al. (2012) developed the Neurofibromatosis 2 Impact on Quality of Life (NFTI-QoL) questionnaire to assess health-related QoL in NF2-Patients with SWN. This eight-item questionnaire assesses various disease-specific domains, such as balance, hearing, facial weakness, vision, mobility/walking, role/perspective in life, pain, and anxiety/depression. Each item consists of a four-point scale ranging from 0 to 3, with 3 being the most impaired. The maximum total score is 24; the higher the NFTI-QoL score, the worse the outcome. The German version (NFTI-QoL-D) demonstrated metric properties comparable to those of the English version9.
Mental health issues
Symptoms of depression
The nine-item Patient Health Questionnaire (PHQ-9) is a survey developed for the treatment of depression14. Each of the PHQ-9 items is quantified on a four-point Likert scale (0 = “not at all”—3 = “almost every day”). The total score ranges from 0 to 27, with 0 indicating no depressive symptoms and 27 indicating that all symptoms occur almost daily.
The PHQ-9 has excellent test-retest reliability and excellent criterion and construct validity14. Internal consistency was confirmed (Cronbach’s α = 0.89). In addition, threshold scores exist to identify different levels of depression severity, including minimal (0–4), mild (5–9), moderate (10–14), moderately severe (15–19), and severe (≥ 20) depression. A score ≥ 10 has been shown to have 88% sensitivity and 88% specificity for major depression in the general medical population14.
Symptoms of anxiety
The Generalized Anxiety Disorder Questionnaire (GAD-7) is a seven-item scale developed to assess symptoms of generalized anxiety disorder15. Items are rated on a four-point Likert scale (0 = “not at all”—3 = “almost every day”). The GAD-7 items describe some of the most important diagnostic criteria for generalized anxiety disorder (ie, feeling nervous, anxious, or on edge, and worrying too much). The total score ranges from 0 to 21, with higher scores indicating more severe symptoms of generalized anxiety disorder. Studies have shown that the GAD-7 is a valid screening tool for generalized anxiety disorder and for assessing its severity in clinical practice and research15,16. The GAD-7 also assigns threshold scores for different levels of severity: minimal (0–4), mild (5–9), moderate (10–14), and severe (15–21) anxiety symptoms. A total GAD-7 score ≥ 10 represents a moderate to severe level of generalized anxiety and is indicative of a suspected diagnosis of generalized anxiety disorder. The GAD-7 showed good sensitivity (89%) and specificity (82%) for detecting generalized anxiety disorder in primary care patients, and its internal consistency was excellent (Cronbach’s α = 0.92).
Somatic symptoms
Somatic symptom severity was measured using the Somatic Symptom Scale (SSS-8), a self-report questionnaire. The SSS-8 was developed as an abbreviated eight-item version of the PHQ-15 to assess the presence and severity of general somatic symptoms17. The SSS-8 assesses the severity of the following somatic symptoms experienced by the respondent during the past seven days: (1) stomach or bowel problems; (2) back pain; (3) pain in arms, legs, or joints; (4) headache; (5) chest pain or shortness of breath; 6) dizziness; (7) feeling tired or lacking energy; and (8) sleep problems. Each item is quantified on a five-point Likert scale (0 = “not at all”—4 = “very much”). The total score ranges from 0 to 32, with higher scores indicating more somatic symptoms. Severity threshold scores define five different levels of somatic symptom severity: not to minimal (0–3), low (4–7), medium (8–11), high (12–15), and very high (16– 32) somatic symptoms. High somatic symptom severity is the case between the 95th and 98th percentile. The German version of the SSS-8 has been validated in the general German population18.
Psychological factors
Sustainability
The 13-item Resilience Scale (RS-13) quantifies resilience on a seven-point scale19. Individuals rate different statements (from 1 = “Disagree” to 7 = “Strongly agree”). The RS-13 is a short German version of the RS-2520. Scores range from 13 to 91, with higher scores indicating greater resilience. Based on the reference groups, individuals with < 72 points on the Resilience Scale (RS-13) were defined as low-resilience individuals. Highly resistant individuals have scores ≥ 7219.
the loneliness
The Rock of Loneliness21 consists of three items introduced by “How often do you feel…”: (1) “…that you miss friendship?”; (2) “…dropped?”; (3) “…isolated from others?”. Items are rated on a five-point Likert scale (0 = “never” to 4 = “very often”). Responses are summed to obtain a total score of 0–12, with higher scores indicating a higher level of loneliness. The German version of the three-item Loneliness Scale was validated in a representative sample and normal values were reported22.
Personality functioning
Personality functioning describes a person’s abilities in four domains related to cognition/perception, regulation, communication, and attachment23. Individuals with impaired personality functioning tend to suffer from severe disturbances of self and their interpersonal relationships and have an increased risk of developing mental disorders such as depression and anxiety24. Personality functioning was measured with the short version of the Operationalized Psychodynamic Diagnosis-Structure Questionnaire (OPD-SQS)25. This is a self-report questionnaire to screen for personality dysfunction26. The OPD-SQS consists of a 0–4 Likert scale (0 = “strongly disagree” to 4 = “strongly agree”). It measures three highly correlated subscales: self-perception, interpersonal contacts, and relationship pattern. The total score ranges from 0 to 48. Lower OPD-SQS scores indicate better personality functioning, while higher OPD-SQS scores indicate impaired personality functioning.
statistical analyses
Data analyzes were performed using IBM SPSS (version 20). Since single values were missing from the questionnaires, the mean substitution method was applied. Isolated single missing values in the questionnaires were replaced using the rounded individual means of the corresponding questionnaires. This was done once for each case for the PHQ-9, SSS-8, and OPD-SQS. Patients with more missing items in the same questionnaire were excluded from the questionnaire analysis. This was done once for each case for GAD-7 and SSS-8. Missing values in the NFTI-QoL-D were replaced by rounded means. Descriptive statistics were calculated for age, sex, NF2-Related to SWN QoL, depression, anxiety, somatic symptoms, resilience, loneliness and personality function.
First, Pearson correlations between different variables were calculated to examine associations. Second, a stepwise hierarchical linear regression analysis was performed. This involved determining NF2-Related to SWN QoL as a dependent variable. Three groups of variables served as predictors and were entered stepwise into the equation. The first predictors were disease severity score and gender. In step 2, values of resilience, loneliness, and personality functioning were entered stepwise as potential psychological predictors. The third group of variables included scores for depression, anxiety, and somatic symptoms as indicators of mental health problems, which were also entered stepwise. Adjusted R squares (R2) and standardized regression coefficient (β). Results were considered significant at p< 0.05.
