Kraepelin (1923) ) and then Bleuler (1949), were the first authors to describe in epilepsy a pleomorphic pattern of symptoms, including affective symptoms with prominent irritability intermixed with euphoric mood, fear, anxiety as well as anergia, pain and insomnia. Gastaut et al. (1955) confirmed Kraepelin s and Bleulers observations, leading Blumer to coin the term interictal dysphoric disorder (IDD) to refer to this type of depressive disorder in epilepsy (Blumer, 2000). Blumers description of the IDD is particularly intriguing. It is characterized by eight key symptoms grouped in three major categories (Table 5.1): labile depressive symptoms (depressive mood, anergia, pain, insomnia), labile affective symptoms (fear, anxiety), and supposedly "specific" symptoms (paroxysmal irritability, euphoric moods). Blumer preferred the term "dysphoria" to more accurately translate the original definition of Kraepelin " Verstimmungszustand" to stress the periodicity of mood changes of the patients and the presence of irritability and outbursts of aggressive behavior as key symptoms. The dysphoric episodes are described as occurring without external triggers and without clouding of consciousness.
TABLE 5.1 Main symptoms clusters of the interictal dysphoric disorder
Labile depressive symptoms Labile affective symptoms Specific symptoms
Depressed mood Fear Euphoric moods
Anergia Anxiety Paroxysmal irritability
They begin and end rapidly and recur fairly regularly in a uniform manner, occurring every few days to every few months and lasting a few hours up to 2 days.
The theoretical framework suggested by Blumer goes beyond a narrow IDD profile, and he speculated that affective symptoms in epilepsy exist along a continuum, from a dysphoric disorder with fleeting symptoms, to a more severe disorder with transient psychotic features, to an even more debilitating disorder with prolonged psychotic states. This scenario is deeply influenced by classic German psychiatry, especially Kraepelin s view of the relationship between manic-depressive illness and schizophrenia (Kraepelin, 1923).
It is obvious that the IDD can be recognized today with features that are different from those described by premodern psychiatry. For example, depressed mood and anergia may be much more evident than before because modern antiepileptic medications may accentuate the dysphoric symptoms. Himmelhoch (1984); and subsequently Kanner and Balabanov (2002), highlighted the chronic course of this state of moderate neurotic depression with symptom-free intervals typical of epilepsy, referring to a dimension very close to dysthymia. In our opinion, IDD patients have several features in common with a specific subset of cyclothymic subjects, where depressive periods and labile-angry-irritable moods dominate the clinical picture. Nonetheless, Blumer reported that patients with IDD benefit from a combined therapy of AEDs and antidepressant drugs (Blumer et al., 2004), a combination extensively used in psychiatry in bipolar depression, suggesting that IDD is close to the bipolar spectrum. It is, therefore, evident that the features of IDD overlap with a variety of affective disorders seen in clinical psychiatric practice, but the concept needs to be further defined in terms of semiology and clinical description (Figure 5.1). In a recent study, we investigated prevalence and psycho-pathological features of IDD in patients with epilepsy compared with a group of patients with migraine (Mula et al., 2008). Our data suggest that IDD is a robust construct and can be diagnosed in a significant proportion of patients (about 20%), being one of the most frequent mood disorders in epilepsy. Nevertheless, it seems that IDD is not typical only of patients with seizure disorders but can be seen also in other central nervous system (CNS) disorders such as migraine with the same prevalence. This concept was partly suggested by Blumer himself, stating that IDD can occasionally occur in the absence of clinical seizures in patients with
brain lesions (with or without an abnormal EEG) (Blumer et al., 1988) . However, further studies are needed to clarify whether IDD is really epilepsy-related or relates to the typical phenomenology of affective disorders in chronically ill populations or better, whether IDD is an organic affective disorder syndrome.
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