اختلال پانیک: نقش سیستم تعادل

Experimental evidences suggest that Panic Disorder (PD) is characterized by abnormalities in respiratory and vestibular functions. We studied balance system function in patients with PD and its relationships with CO2 reactivity and clinical characteristics. Nineteen patients with PD with/without agoraphobia underwent static posturography and the 35% CO2 challenge. The severity of clinical symptomatology was measured by standardized psychometric scales. Patients were free of psychotropic medications during the 2 weeks before the study. Different investigators blind to each other carried out the CO2 challenge, static posturography and clinical assessment. Nineteen age and sex-matched healthy controls underwent static posturography. Body sway velocity and length were significantly higher in panic patients than in controls and patients showed high percentages of abnormal scores. Patients with two or more abnormal scores on static posturography were significantly more agoraphobic than those with less than two. Abnormal posturography scores under the eyes-opened was related to high anticipatory anxiety, whereas those under eyes-closed was related to phobic avoidance. Symptomatological reactivity to CO2 was significantly correlated to abnormal functions of the balance system in the eyes-closed condition. Our findings suggest that (1) many patients with PD (5–42%) have abnormalities in their balance system function compared with healthy controls (0–5%), (2) symptomatological reactivity to CO2 and balance system function in patients with PD are correlated only in the eyes-closed condition and (3) there is a significant link between agoraphobic avoidance and subclinical abnormal function of the balance system network.

Significant relationships between balance function disorders and panic disorder (PD) has been repeatedly reported (27, 28, 29, 48, 12, 14, 25, 50, 52, 53, 16, 19 and 2). The studies into these relationships have focused on two main areas: vestibular abnormalities in patients with PD, and anxiety symptoms or disorders among patients with abnormalities in the vestibular system. Jacob and co-workers (26 and 28) reported vestibular abnormalities in patients with PD who complained of dizziness. This finding has been replicated in patients with PD non-specifically selected for the presence of dizziness (48, 25 and 32), where the abnormalities were not the expression of a full-blown vestibular disorder. Similarly, patients with vestibular disorders have psychiatric syndromes with a particular reference to PD and agoraphobia (Hallam and Stephens, 1985). Yardley and co-workers (1995) reported an association between vestibular abnormalities and phobic avoidance. Jacob and co-workers (1996) showed that patients with PD and agoraphobia had more vestibular abnormalities than patients with PD but without agoraphobia, patients with depressive disorders or with anxiety disorders other than panic or healthy controls. We (Allevi et al., 1997) found a significant relationship between the presence of dizziness during panic attacks and agoraphobia. It seems that in some patients phobic avoidance might not be a mere consequence of panic attacks but rather the result of a more complex interaction. Abnormalities in the respiratory function may play a central role in the pathogenetic mechanisms underlying PD and has been mainly associated with panic attacks (34 and 8). Some observations have indicated that the vestibular and the respiratory systems may work in complex interrelationships with one another. Dizziness is one of the main symptoms induced by CO2 inhalations (Perna et al., 1994a) and by hyperventilation (Fried and Grimaldi, 1993). Balance and respiratory systems seem to influence two different aspects of panic disorder, respectively agoraphobia and panic attacks. Control centers of both, however, are located nearby in the brainstem with significant reciprocal influences and there is evidence of vestibular-respiratory functional interconnections (Furman et al., 1998). We hypothesize that balance function might play a role in the development of agoraphobia and that respiratory reactivity might influence this process. To test this hypothesis we evaluated the balance system function by posturography and respiratory reactivity by CO2 inhalation test in a sample of patients with PD.