Digital Patient-Reported Outcome Measures Assessing Health-Related Quality of Life in Skull Base Diseases—Analysis of Feasibility and Pitfalls Two Years after Implementation

Health-related quality of life (HRQoL) assessment is becoming increasingly important in neurosurgery following the trend toward patient-centered care, especially in the context of skull base diseases. The current study evaluates the systematic assessment of HRQoL using digital patient-reported outcome measures (PROMs) in a tertiary care center specialized in skull base diseases. The methodology and feasibility to conduct digital PROMs using both generic and disease-specific questionnaires were investigated. Infrastructural and patient-specific factors affecting participation and response rates were analyzed. Since August 2020, 158 digital PROMs were implemented in skull base patients presenting for specialized outpatient consultations. Reduced personnel capacity led to significantly fewer PROMs being conducted during the second versus (vs.) the first year after introduction (mean: 0.77 vs. 2.47 per consultation day, p = 0.0002). The mean age of patients not completing vs. those completing long-term assessments was significantly higher (59.90 vs. 54.11 years, p = 0.0136). Follow-up response rates tended to be increased with recent surgery rather than with the wait-and-scan strategy. Our strategy of conducting digital PROMs appears suitable for assessing HRQoL in skull base diseases. The availability of medical personnel for implementation and supervision was essential. Response rates during follow-up tended to be higher both with younger age and after recent surgery.


Introduction
During the recent shift from disease-centered to patient-centered medical care, the assessment of health-related quality of life (HRQoL) has become increasingly important [1,2]. In the context of individualized care, patients are involved in medical decision-making processes [3]. "Shared decision making" is applied in surgical disciplines, for example, when different therapeutic options are available that are considered to be equivalent, or during the monitoring of so-called "incidental findings" [4,5]. In the field of neurosurgery, this concept appears to be of central relevance for the management of skull base pathologies. Considering the mainly benign tumors in this region, a wait-and-see strategy must often be weighed against various therapeutic approaches. These individual decision-making processes require not only knowledge about the natural course of the disease and the outcome to be expected with treatment, but also awareness of HRQoL and disease-specific factors in

Study Design
Systematic assessment of HRQoL using digital PROMs (Heartbeat Medical, HRTBT Medical Solutions GmbH, Berlin, Germany) was performed in the Department of Neurosurgery, a tertiary referral center specialized in skull base diseases, since August 2020. The purpose of the current retrospective study is to analyze factors that potentially influence participation in digital PROMs and response rates during follow-up assessments. In this context, the infrastructural aspects (e.g., availability of medical staff, the selection of questionnaires, and the potential impact of the COVID-19 pandemic) and patient-specific factors (e.g., age, type of disease, and clinical procedure) are investigated. The study intends to identify possible difficulties and pitfalls that require optimization to enable routine use of PROMs in the care of skull base diseases. Inclusion criteria were as follows: age ≥ 18 years, presence of a neurosurgical skull base disease, presentation to the outpatient clinic, and consent to participate in digital PROMs. Exclusion criteria were as follows: age < 18 years, presence of other than neurosurgical skull base disease, and lack of consent to participate. Informed consent to data collection and storage was obtained from patients with their participation in digital PROMs by medical staff in the outpatient clinic. The retrospective analysis was approved by the independent ethics committee of our medical center (reference no. 22-1295-S1-retro, 9 August 2022) and is reported according to institutional guidelines.

Implementation of PROMs
Digital PROMs were implemented in 158 adult patients with skull base pathologies during outpatient visits, following a sophisticated protocol, with selection of questionnaires depending on the underlying disease and localization of the process. All questionnaires were administered in their standardized, validated German versions. Participants with insufficient language skills could be supported by accompanying persons or use smart-phone tools for translation. Patients presented either for consultation after first diagnosis, for planning of a surgery, or for regular follow-up visits (i.e., check-ups after treatment or monitoring as part of wait-and-scan strategies). The initial PROM assessments were completed during outpatient visits using tablets (the initial assessments are referred to as T1). Persons with visual or other neurological impairment may have had to be assisted by an accompanying person to carry out the assessment. With consent to further follow-up assessments, patients received the same questionnaires automatically by email after 3 and 12 months (referred to as T2 and T3, respectively). In case of non-response, reminder emails were sent automatically by the system at fixed intervals. Patients had the option to unsubscribe from the system via a link included in the follow-up emails. The results of the questionnaires were transferred and stored in the hospital's internal system with the patients' electronic medical records.

Disease-Specific Selection of Questionnaires
Prior to implementation of PROMs, the following subgroups were defined for selection of questionnaires according to the underlying disease and localization of the process: In all three subgroups (together referred to as "group ALL"), assessment of general HRQoL and comorbidities was conducted with three standardized questionnaires: EQ-5D-5L/EQ-5D-VAS, 15D, and Self-Administered Comorbidity Questionnaire (SCQ). To determine specific problems associated with the underlying disease or its localization, additional questionnaires were administered in subgroups AMSB and CPA. The National Eye Institute Visual Function Questionnaire (NEI-VFQ-25) was implemented in subgroup AMSB to evaluate the influence of visual dysfunction. To assess the potential impact of hearing impairment, dizziness, and facial nerve dysfunction in subgroup CPA, the Penn Acoustic Neuroma Quality of Life (PANQOL) scale, the Dizziness Handicap Inventory (DHI), the Facial Disability Index (FDI), and the Facial Clinimetric Evaluation (FaCE) were included. In subgroup NVC, the Patient Satisfaction Index (PSI) was added to measure treatment satisfaction.

Statistical Analysis
Methods of descriptive statistics were used. Categorical data are presented as absolute and relative frequencies (in %). For numerical data, either mean values with standard deviation (SD) or median values with minimum/maximum and interquartile range (IQR) were calculated, as required. Statistical differences were evaluated using the t test or Mann−Whitney test, as appropriate. The level of significance was set at p < 0.05. Statistical analysis was performed using GraphPad Prism software version 9.4.1 for Mac (GraphPad Software, San Diego, CA, USA).

Availability of PROMs and Participation Rate
In the current study, we analyzed the 24 months (August 2020-July 2022) since digital PROMs were implemented in the Department of Neurosurgery to assess HRQoL in patients with skull base diseases. During this period, special consultation hours for skull base diseases were held in our outpatient clinic on 96 days ("skull base consultation day" = SBCD), on which a total of 1120 skull base patients presented (mean: 11.7 patients per SBCD). Conducting PROMs required the capacity of the outpatient medical staff, who had to register patients in the system, instruct and support them in (technical) performance, and manage the hardware. Therefore, the capacity for PROMs was dependent on staff availability; it was not always possible to conduct PROMs, and they were frequently applied with reduced capacity. Overall, PROMs were performed on 51 SBCDs during the analysis period, while the offer to participate was made to every patient presenting on 16 SBCDs (participation rate of 53.55%) and only to patients presenting for the first time (after initial diagnosis or before/after surgery) on 35 SBCDs (participation rate of 63.83%). Further information is given in Figure 1.
In the current study, we analyzed the 24 months (August 2020−July 2022) since digital PROMs were implemented in the Department of Neurosurgery to assess HRQoL in patients with skull base diseases. During this period, special consultation hours for skull base diseases were held in our outpatient clinic on 96 days ("skull base consultation day" = SBCD), on which a total of 1120 skull base patients presented (mean: 11.7 patients per SBCD). Conducting PROMs required the capacity of the outpatient medical staff, who had to register patients in the system, instruct and support them in (technical) performance, and manage the hardware. Therefore, the capacity for PROMs was dependent on staff availability; it was not always possible to conduct PROMs, and they were frequently applied with reduced capacity. Overall, PROMs were performed on 51 SBCDs during the analysis period, while the offer to participate was made to every patient presenting on 16 SBCDs (participation rate of 53.55%) and only to patients presenting for the first time (after initial diagnosis or before/after surgery) on 35 SBCDs (participation rate of 63.83%). Further information is given in Figure 1.

Conduction of PROMs in Relation to the COVID-19 Pandemic
The analysis period included the 2nd, 3rd, and 4th wave of the COVID-19 pandemic. According to the German Federal Statistical Office, the 2nd, 3rd and 4th wave covered a total period of 13 months. During this period, the mean number of patients presenting was 11.48 per SBCD; in the 11 months beyond COVID-19 waves, it was 11.89 per SBCD. The mean number of consultations remained relatively stable during the 24 months, except during the 2nd wave, when it was significantly reduced (see Figure 2). As a result of staff unavailability, PROMs could not be offered during COVID-19 waves on a total of 22 SBCDs (mean: 1.69/month) and beyond COVID-19 waves on a total of 23 SBCDs (mean: 2.09/month). Independent of the pandemic, when comparing the first (August 2020−July 2021) and second (August 2021−July 2022) year after implementation, no PROMs could be offered on 15 SBCDs during the first year (mean: 1.25/month) and on 30 SBCDs during the

Conduction of PROMs in Relation to the COVID-19 Pandemic
The analysis period included the 2nd, 3rd, and 4th wave of the COVID-19 pandemic. According to the German Federal Statistical Office, the 2nd, 3rd and 4th wave covered a total period of 13 months. During this period, the mean number of patients presenting was 11.48 per SBCD; in the 11 months beyond COVID-19 waves, it was 11.89 per SBCD. The mean number of consultations remained relatively stable during the 24 months, except during the 2nd wave, when it was significantly reduced (see Figure 2). As a result of staff unavailability, PROMs could not be offered during COVID-19 waves on a total of 22 SBCDs (mean: 1.69/month) and beyond COVID-19 waves on a total of 23 SBCDs (mean: 2.09/month). Independent of the pandemic, when comparing the first (August 2020-July 2021) and second (August 2021-July 2022) year after implementation, no PROMs could be offered on 15 SBCDs during the first year (mean: 1.25/month) and on 30 SBCDs during the second year (mean: 2.5/month) due to staff unavailability. The mean number of completed PROMs per SBCD did not differ significantly when comparing the period during and beyond COVID-19 waves (1.89 vs. 1.34 per SBCD, respectively). However, the mean number of completed PROMs per SBCD was significantly reduced during the second year after implementation when compared with the first year (0.77 vs. 2.47 per SBCD, respectively; p = 0.0002). Further details are listed in Figure 2.
second year (mean: 2.5/month) due to staff unavailability. The mean number of comple PROMs per SBCD did not differ significantly when comparing the period during and yond COVID-19 waves (1.89 vs. 1.34 per SBCD, respectively). However, the mean num of completed PROMs per SBCD was significantly reduced during the second year af implementation when compared with the first year (0.77 vs. 2.47 per SBCD, respective p = 0.0002). Further details are listed in Figure 2. Comparison of the mean number (with sta ard deviation) of (A) consultations per "skull base consultation day" (SBCD) or of (B) comple PROMs per SBCD (in relation to the total of 96 SBCDs), illustrated for the 13 months during COV 19 waves ("all waves" or subdivided into "second wave" (2nd wave), "third wave" (3rd wave), a "fourth wave" (4th wave)) and the 11 months beyond COVID-19 waves ("no wave"), and illustra for the "first year" (1st year) and "second year " (2nd year) after implementation of PROMs.
Of the 158 patients who had completed T1, 39 (24.7%) underwent surgery betwe T1 and T2, 59 (37.3%) followed a wait-and-scan strategy, and 60 (38.0%) had already u dergone surgery before T1 (19 within the last 6 months). The response rate during follo up was highest in patients who underwent surgery between T1 and T2, where 25 Comparison of the mean number (with standard deviation) of (A) consultations per "skull base consultation day" (SBCD) or of (B) completed PROMs per SBCD (in relation to the total of 96 SBCDs), illustrated for the 13 months during COVID-19 waves ("all waves" or subdivided into "second wave" (2nd wave), "third wave" (3rd wave), and "fourth wave" (4th wave)) and the 11 months beyond COVID-19 waves ("no wave"), and illustrated for the "first year" (1st year) and "second year " (2nd year) after implementation of PROMs.  Figure 3. ALL = total group; AMSB = subgroup "anterior and middle skull base"; CPA = subgroup "cerebellopontine angle"; NVC = subgroup "neurovascular conflict"; no. = number; n = number of completed questionnaires; T1 = initial assessment; T2 = follow-up assessment after 3 months; T3 = follow-up assessment after 12 months; "surgery between T1 and T2" = surgical treatment was performed after the initial assessment and before the follow-up assessment after 3 months; "previous surgery before T1" = surgical treatment had already been performed before the initial assessment; § = in 10/29 (  . Evaluation of the response rate to PROMs depending on subgroup and neurosurgical procedure. ALL = total group, AMSB = subgroup "anterior and middle skull base", CPA = subgroup "cerebellopontine angle", NVC = subgroup "neurovascular conflict", no. = number, T1 = initial assessment, T2 = follow-up assessment after 3 months, T3 = follow-up assessment after 12 months, "surgery after T1" = surgical treatment was performed after the initial assessment and before the follow-up assessment after 3 months, "wait-and-scan" = wait-and-scan strategy, "surgery before T1" = surgical treatment had already been performed before the initial assessment.

Response Rate to PROMs Depending on Age
The mean age of group ALL at T1 was 58.39 years (y), and those of subgroups AMSB and CPA was 58.67 y and 55.23 y, respectively. The mean age of subgroup NVC was significantly higher at 67.71 y, compared with both group ALL (p = 0.0033) and subgroups AMSB (p = 0.0071) and CPA (p = 0.0002) (see Figure 4A). Both in group ALL and in sub- Figure 3. Evaluation of the response rate to PROMs depending on subgroup and neurosurgical procedure. ALL = total group, AMSB = subgroup "anterior and middle skull base", CPA = subgroup "cerebellopontine angle", NVC = subgroup "neurovascular conflict", no. = number, T1 = initial assessment, T2 = follow-up assessment after 3 months, T3 = follow-up assessment after 12 months, "surgery after T1" = surgical treatment was performed after the initial assessment and before the follow-up assessment after 3 months, "wait-and-scan" = wait-and-scan strategy, "surgery before T1" = surgical treatment had already been performed before the initial assessment.

Response Rate to PROMs Depending on Age
The mean age of group ALL at T1 was 58.39 years (y), and those of subgroups AMSB and CPA was 58.67 y and 55.23 y, respectively. The mean age of subgroup NVC was significantly higher at 67.71 y, compared with both group ALL (p = 0.0033) and subgroups AMSB (p = 0.0071) and CPA (p = 0.0002) (see Figure 4A). Both in group ALL and in subgroup AMSB, the mean age of patients who completed T3 (T3 pos) was significantly lower compared with the baseline (T1 pos) (group ALL: 54.11 vs. 58.39 y (p = 0.0322) and subgroup AMSB: 52.19 vs. 58.67 y (p = 0.0346)) and compared with those not completing T3 (T3 neg) (group ALL: 54.11 vs. 59.90 y (p = 0.0136) and subgroup AMSB: 52.19 vs. 62.09 y (p = 0.0023)). The mean age according to completion of follow-up assessments is given in Figure 4B,C.     AMSB, 53/69 (76.8%) were female and 16/69 (23.2%) were male; in contrast, subgroup CPA was more balanced, with 38/68 (55.9%) females and 30/68 (44.1%) males. In subgroup AMSB, higher response rates for T2 and T3 were observed among females, whereas in subgroup CPA, higher response rates for T2 and T3 were observed among males. Detailed information is presented in Figure 5.

Discussion
The trend toward patient-centered medical care implies an increasing impact of factors, such as symptom burden, functional status, and HRQoL on individual treatment decisions [21][22][23]. These parameters can be systematically assessed in routine clinical practice through the use of PROMs, with digital formats providing increased accessibility and simplification of data collection [4,24]. In neurosurgery, assessing HRQoL and diseasespecific symptoms is essential in the field of skull base tumors, as the long-term outcome of these usually benign lesions with potential involvement of neurovascular structures has to be considered in treatment decisions [15,25,26]. The complementary effect of using both generic and specific questionnaires needs to be emphasized; however, reports on the application of disease-specific questionnaires in skull base tumors are scarce [27,28]. The current study presents the first experiences and pitfalls of an elaborate strategy to assess HRQoL using digital PROMs in a tertiary care center specialized in skull base diseases, following a sophisticated protocol including validated and well-established, both generic and disease-specific questionnaires.

Availability of PROMs and Participation Rate
The inclusion of individual patient-specific factors in decision-making processes requires the compliance of those affected to obtain representative results. It is generally distinguished between personal characteristics of non-participants and individual reasons for nonparticipation [29]. The literature is scarce regarding descriptions of personal characteristics of non-participants, although two studies observed an emphasis on female gender [29][30][31]. In contrast, numerous reasons for non-participation are reported that reflect the results of our study [30]. For example, studies listed "health problems" and "old age" as reasons for non-participation, as they impeded participation due to problems with handling or cognition [30,[32][33][34]. These problems were also identified in our data, which were labeled "cognitive impairment/age/lack of vision". Beside "language barrier" as another reason, "lack of engagement" is also found in the literature, suggesting that patients feel "not sick enough" to participate or do not see a personal benefit [20,30,31,35,36]. "Lack of engagement" might have been a factor in our study when patients did not participate for "unknown reasons". Inconsistent staff availability with inconsistent ability to implement PROMs may also have affected personal engagement and, thus, influenced the decision Figure 5. Evaluation of the response rate to PROMs depending on gender. ALL = total group, AMSB = subgroup "anterior and middle skull base", CPA = subgroup "cerebellopontine angle", NVC = subgroup "neurovascular conflict", no. = number, T1 = initial assessment, T2 = follow-up assessment after 3 months, T3 = follow-up assessment after 12 months. (A,B): Number of completed assessments T1, T2, and T3 in relation to gender among ALL (A) and the subgroups AMSB (B1), CPA (B2), or NVC (B3) (the proportion of completed T2/T3 assessments in relation to the corresponding number of T1 assessments, sorted by gender, is presented as a percentage).

Discussion
The trend toward patient-centered medical care implies an increasing impact of factors, such as symptom burden, functional status, and HRQoL on individual treatment decisions [21][22][23]. These parameters can be systematically assessed in routine clinical practice through the use of PROMs, with digital formats providing increased accessibility and simplification of data collection [4,24]. In neurosurgery, assessing HRQoL and diseasespecific symptoms is essential in the field of skull base tumors, as the long-term outcome of these usually benign lesions with potential involvement of neurovascular structures has to be considered in treatment decisions [15,25,26]. The complementary effect of using both generic and specific questionnaires needs to be emphasized; however, reports on the application of disease-specific questionnaires in skull base tumors are scarce [27,28]. The current study presents the first experiences and pitfalls of an elaborate strategy to assess HRQoL using digital PROMs in a tertiary care center specialized in skull base diseases, following a sophisticated protocol including validated and well-established, both generic and disease-specific questionnaires.

Availability of PROMs and Participation Rate
The inclusion of individual patient-specific factors in decision-making processes requires the compliance of those affected to obtain representative results. It is generally distinguished between personal characteristics of non-participants and individual reasons for non-participation [29]. The literature is scarce regarding descriptions of personal characteristics of non-participants, although two studies observed an emphasis on female gender [29][30][31]. In contrast, numerous reasons for non-participation are reported that reflect the results of our study [30]. For example, studies listed "health problems" and "old age" as reasons for non-participation, as they impeded participation due to problems with handling or cognition [30,[32][33][34]. These problems were also identified in our data, which were labeled "cognitive impairment/age/lack of vision". Beside "language barrier" as another reason, "lack of engagement" is also found in the literature, suggesting that patients feel "not sick enough" to participate or do not see a personal benefit [20,30,31,35,36]. "Lack of engagement" might have been a factor in our study when patients did not participate for "unknown reasons". Inconsistent staff availability with inconsistent ability to implement PROMs may also have affected personal engagement and, thus, influenced the decision not to participate. As "personal reasons", factors such as "data security and trust" (i.e., concerns about the digital format), "technical issues" (lack of hardware/software or lack of technical skills), and "emotional distress" (e.g., patients do not want to be reminded of their illness by follow-up interviews) can be found both in the literature and in our analysis [30,35,[37][38][39][40][41].

Conduction of PROMs in Relation to the COVID-19 Pandemic
During COVID-19 pandemic peaks, the demand for specialized neurosurgical consultations remained high, as demonstrated by our analysis over 2 years. Comparing the 13 months covered by COVID-19 waves and the 11 months beyond, there were no relevant differences regarding the capacity of medical staff to implement PROMs or (what depends on it) the mean number of completed PROMs per SBCD. However, there were significant differences when comparing these aspects between the first and second year after implementation of PROMs, independent from COVID-19 waves. The number of SBCDs where PROMs could not be implemented due to staff unavailability was twice as high in the second year compared with the first year; consequently, the mean number of PROMs completed per SBCD was significantly reduced in the second year. This implies a certain bias in data collection, as the implementation of PROMs was thus significantly influenced by the availability of personnel. It can be assumed that more PROMs could have been implemented if staff had been available, and that many people who would have wished to participate did not have the opportunity to do so. Therefore, the availability of medical staff is a crucial factor for initiating PROMs. As this aspect has been identified as a key factor based on our data, intensive efforts should be made to find solutions for the future. If it is not possible to provide more medical staff, scientific staff or students could be involved to support the work, with the aim of consistent data collection and provision for individualized medical care. Several reports published in 2022 pointed to a progressive decline in medical staff availability in the aftermath of the COVID-19 pandemic [42,43]. In addition to the immediate negative effects on maintaining patient care, also long-term adverse effects on future healthcare quality are to be expected.

Response Rate to PROMs Depending on Subgroup and Neurosurgical Procedure
The current analysis revealed a response rate of 52.5% at 3-month follow-up and of 38.6% at 12-month follow-up. Few similar studies on the use of PROMs in skull base diseases can be found in the literature, and no comparable data on response rates are available. Several reports describe the assessment of the general HRQoL or the development of specific questionnaires for application in certain skull base diseases [6,7,14,44]. A review by Nielsen et al. of 51 studies reported high variance in dropout rates regarding the general application of PROMs in medicine, where a high dependency on the underlying disease and the conducted treatment can be assumed [29]. Most patients who completed T1 were affected by benign tumors and were equally distributed among the subgroups AMSB (43.7%) and CPA (43.0%). There were no relevant differences in response rates during follow-up between these subgroups. Thus, it was neither observed that response rates depended on specific diseases or (localization-related) neurological deficits, nor, for example, that the higher amount of specific questionnaires (PANQOL, DHI, FDI, and FaCE) in subgroup CPA had a negative "lack of engagement"effect on compliance in completing follow-up.
Among 158 patients, 24.7% underwent surgery between T1 and T2, 37.3% followed a wait-and-scan strategy, and 38.0% had already undergone surgery before T1. Patients who underwent surgery after T1 had the highest response rates during follow-up (T2: 64.1% and T3: 53.8%), assuming that patients' motivation in the immediate context of treatment is high and that recent surgery as a major event is strongly present in their mind. This might create a selection bias for patients who underwent surgery between T1 and T2, which could lead to an overall overrepresentation of this group. However, in the context of recent surgery, there are also certain conditions that may prevent participation or influence the results, such as complications requiring additional treatment, re-admission to hospital, or mortality. These circumstances are of special importance for the interpretation of the results of questionnaires. At 3-month follow-up, the response rate among patients following a wait-and-scan strategy (52.5%) was slightly higher than that among patients having undergone surgery before T1 (45.0%). At 12-month follow-up, patients following a wait-and-scan strategy had lower response rates (28.8%) compared with those having undergone surgery before T1 (38.3%). This might be attributed to the effect described in the literature, where patients affected by asymptomatic "incidental findings" may have less mental focus on the disease, feel "not sick enough", or see less personal benefit from participating [30,31,35]. In contrast, after having undergone surgery as a "life event", a disease may be more mentally present in the long-term, resulting in higher motivation to attend follow-up assessments. The knowledge of patient-specific factors appears to be essential in wait-and-scan strategies, where decision making about a need for treatment must be repeated regularly. Therefore, the importance of performing follow-up PROMs should be emphasized in patients following wait-and-scan strategies. As a consequence of our analysis, efforts should be made to provide additional staff resources to regularly monitor response rates and, in case of non-response, to try to increase response rates through personal contact and motivation.

Response Rate to PROMs Depending on Age
The present analysis revealed a significantly lower mean age of patients who completed T3 compared with the total number of patients who completed T1 and those who did not complete T3. Thus, there appears a correlation between older age and a lower response rate during follow-up, which is also described in the literature [30,[32][33][34]. This also suggests an association with the digital format, as older people are more likely to lack technical tools and skills. Consequently, there might be a risk for older people to be underrepresented by the application of a digital format. Family members or medical staff as support for conducting digital PROMs in elderly people and those with cognitive/visual impairment or other neurological deficits could help to avert the risk of disadvantaging vulnerable groups. As already indicated above, the involvement of scientific staff or students could be helpful for the conduction in these groups. Furthermore, providing questionnaires in different languages seems to be important in this context and should be feasible, especially in digital formats with automated evaluation.

Response Rate to PROMs Depending on Gender
During follow-up, the response rates of male participants were slightly higher than those of female participants, which may be in line with the observation reported in the literature that non-participants were more likely to be female [29][30][31]. However, no critical differences necessitating gender-specific interventions for improvement were identified.

Conclusions
The implementation of digital PROMs for the assessment of HRQoL may provide perspectives in the trend toward individualized patient care, also in the context of (mostly benign) skull base diseases. The current evaluation of our strategy to conduct digital PROMs revealed high response rates during follow-up, with no significant differences regarding gender, and a trend for best response rates associated with recent surgery. Older age was frequently a reason for non-participation and was a significant risk factor for not completing follow-up assessments. The lack of medical personnel was found to be the key problem preventing a widespread implementation and supervision of digital PROMs, particularly for enhanced disease-specific protocols. Reduced staff capacity in our analysis was less of an acute problem during the COVID-19 waves, but rather became apparent as a long-term effect of the pandemic.
Funding: This research received no external funding.

Institutional Review Board Statement:
The study was conducted in accordance with the Declaration of Helsinki and approved by the Institutional Independent Ethics Committee of the Albert-Ludwigs-University Freiburg, Germany (reference no. 22-1295-S1-retro, 9 August 2022).
Informed Consent Statement: Informed consent to data collection and storage was obtained from patients with their participation in digital PROMs.

Data Availability Statement:
The data used to support the findings of this study are available from the corresponding author upon request.