The so-called hidden symptoms or soft signs of multiple sclerosis comprise cognitive dysfunction, fatigue, depression and anxiety. From a patient's perspective, these symptoms are rated as exerting much more negative impact on quality of life and daily functioning than their physical symptoms. Despite this knowledge, the symptoms remain disregarded by many neurologists in clinical practice. This missing awareness can be attributed to several reasons. First, the underlying pathophysiological mechanisms determining occurrence and severity of the different symptoms are still unclear.Second, there is uncertainty in how to reliably assess them. It is undeniable that assessment can be difficult as the hidden symptoms seldom appear isolated but more often highly interact. Third, if standardized, fast and cost-effective assessment to quantify and monitor the evolution of the hidden symptoms would be feasible, the question still remains how to treat these aspects. The present article will give an overview on symptom background and assessment strategies for clinical practice. Fatigue, cognitive dysfunction, depression and anxiety occur among all disease courses in multiple sclerosis (MS) with prevalence rates between 35% and 95% and even in patients with a so-called benign form.1 Due to a strong coincidence and interaction, these symptoms exert a strong negative influence on quality of life (QoL) and vocational status.2 From a patient's perspective, being affected by fatigue and cognitive decline is far from being benign and soft. Concerning the assumption that these symptoms rather remain hidden depends on the eye of the beholder. If you pay enough attention, you will see them very clearly. The only remaining question is how to objectify, classify and quantify them (Fig. 1).
| COGNITIVE IMPAIRMENTCognition represents a central human ability, which refers to a wide range of higher order brain functions such as processing speed, memory, attention, executive functions and learning abilities. In MS, several cognitive domains can be affected, and once started, this impairment is often persistent and progressive. It is of importance to notice that cognitive problems can occur at early stages of the disease, 3 even in patients with clinically isolated syndrome 4 or radiologically isolated syndrome 5 and in paediatric MS as well 6 .The cognitive core deficits in adult MS are verbal and visual shortterm memory and learning, cognitive flexibility/attention and processing speed/fluidity. 7 As these three cognitive domains are highly relevant for daily functioning, patients experience a significant burden and diminished QoL due to reduced self-esteem, loss of social activities and contacts, and reduction or even loss of work responsibilities.
8Although progression of cognitive decline is generally slow, and in this sense different from other neurodegenerative diseases, the most vulnerable phase for progression seems to occur during the first 5 years after disease onset. This indicates that treatment aimed at protecting against cogni...