All three patients presented here had unusual postures when standing. Despite their unsteady postures, they had never fallen while standing or walking, and all had no nystagmus and postural hypotension. Considering this curious phenomenon, astasia without abasia can be similar with this abnormal feature. “Astasia without abasia” is therefore defined as an inability to keep a stationary position although the legs are under control when walking or assuming and maintaining an upright posture. The most common cause of astasia without abasia is peripheral neuropathy.
7 However, our patients presented with some patterns, those differed from classic astasia. We found that some patients had unsteady standing postures during certain of their posture changes: standing up from their chairs, coming to a halt from a walk, or moving forward from a standing start (Case 1 and 3). The patient in Case 2, in particular, experienced a unique symptom; his unsteady posture depended solely on the width of his stance. Although the typical astasia pattern is a known phenomenon among PGDs,
4 this atypical form of astasia without abasia has not been reported to date. Boogaarts et al.
8 reported a patient with a recumbent gait, which they regarded as a variant of astasia-abasia. Unlike the patient in their study, none of our patients experienced any change in symptoms that depended upon whether the eyes were open or closed.
Typically, most patients with PMD have certain characteristic features, including an abrupt onset, inconsistent, incongruent patterns, simultaneous multiple symptoms, and a previous history of minor injury.
2 Our patients had histories that included abrupt onset and incongruent patterns, although Case 1 had an unclear onset of symptoms. Case 1 had a unique underlying brain lesion on the frontal lobe area. Considering that lesion, his bouncing and ataxic features are understandable.
9 The core clinical elements of frontal gait disorders can be characterized as hypokinetic, rigid gait with ataxic, impaired postural reflexes, akinetic and a tendency to fall. In general, cerebrovascular disease of the frontal lobe is a main cause of frontal gait.
9 Early descriptions of frontal gait syndromes emphasized the ataxic elements, because researchers considered involvement of frontopontocerebellar pathways to be the most likely mechanism.
10 In frontal lobe dysfunction, both isolated gait ignition failure and primary progressive freezing gait can be accompanied by normal stepping, once walking is underway, and by preservation of balance and postural reflexes.
11,
12 Patients with frontal lobe abnormalities commonly present with a combination of the above clinical signs, each of which may vary in severity. However, our patient was likely to complain of fluctuating symptoms and other incongruous neurological deficits, including memory loss and dyscalculia, despite their mental functioning being normal.
Actually, PMD is notoriously difficult to diagnosis. We are accustomed to making use of suggestions, distractions, and/or triggering method to differentiate between organic and psychogenic origin. Although placebos can be used to confirm psychogenic disorders, we have to consider that placebos might affect the trust component of the doctor-patient relationship.
13 Fortunately, the placebo affected all of the patients in this study, so we were able to confirm them as having PMD, although one of them had underlying organic abnormalities. Considering the phenomenological aspects of these patients, we might regard them as experiencing a psychogenic balance disorder rather than astasia without abasia of psychogenic origin.