Introduction

About 10% of functional (psychogenic) movement disorders (also called conversion disorders) are related primarily to problems with standing and walking.1–6 They should be diagnosed by demonstrating internal inconsistency and incongruity with disease, but this process can be especially problematic for gait disorders reflected in a higher rate of misdiagnosis than other functional disorders.7 We report two cases of a particular subtype of functional gait disorder, astasia, which were detected because of the effect that iPhone use had on the presenting symptoms. We review previous literature in this area.

Case 1

A 16-year-old boy presented with a 3-day history of balance problems. This began after he fell against a wall after a 1 h period of standing. He had three subsequent falls to the ground with no dizziness, vertigo, weakness or sensory disturbance. If he concentrated hard, or focused intently on something else such as his iPhone, his balance and gait were normal but, ‘If I relax with my mind blank, I fall over.’ He reported chronic insomnia, intermittent low mood and episodes of depersonalisation. He and his family were anxious about a sinister cause.

As he entered the room he was texting on his phone with a normal gait. Neurological examination on the bed was normal. When he stood and ‘let go’ (ie, stopped concentrating), he fell in all directions with no balance corrections. If he looked at his iPhone or attempted to repeat numbers drawn on his back, his standing and walking ability returned to normal. We gave him and his family a positive explanation of functional gait disorder.8 The symptoms resolved completely within 24 h.

Case 2

A 21-year-old woman was referred with a 3-day history of falls and a feeling that she would fall backwards if she stood still. She had a history of anxiety and panic attacks. She had recently stopped taking propranolol. She could maintain her balance most of the time by taking small ‘correction steps’, but had several falls when standing still. Her walking was normal. Each fall was accompanied by a brief dissociative experience of feeling ‘not there’ lasting seconds.

Neurological examination was normal on the bed, but on standing, her knees constantly buckled requiring continual small steps, predominantly backwards, to maintain balance. Her standing returned to normal when playing the game ‘Doodle Jump’ on an iPhone, during eye movement testing or when trying to repeat numbers drawn on her back (see online supplementary video). We gave her a positive explanation of functional gait disorder. Subsequent MR scan of brain was normal, and the symptom resolved after several weeks.

Discussion

Both patients presented with acute onset difficulties in standing still (astasia). A striking feature in both cases was normal balance when they were distracted by another task, such as using a phone. This was one of many signs that these difficulties required focused attention in order to manifest, in keeping with a functional disorder. The diagnosis of a functional balance disorder was further strengthened by the rapid resolution of symptoms following a positive explanation of the diagnosis. The patients needed no other specific interventions.

Normal balance involves the integration of many sensory inputs that occur outside of awareness; however, our attention may be drawn to our balance when the perception of needing to maintain balance is increased, such as by standing near the edge of a high ledge or crossing a log bridge. These patients’ histories are consistent with acute hyper-vigilance of balance, perhaps triggered by presyncope in Case 1. Distraction with an iPhone temporarily reduced this hyper-vigilance, allowing normal automatic standing balance to resume.

Functional disorders of standing (astasia) and walking (abasia) have been classified in different ways. They have several different clinical features, mostly based on distraction or use of a different motor ‘program’ (eg, running or walking backwards). Table 1 shows gait subtypes and clinical features distilled from the main published series.1 ,2 ,3 ,6 These are examples of the positive signs now required to make a diagnosis of conversion disorder (functional neurological symptom disorder) in DSM-5. Our cases are examples of functional astasia with a positive ‘psychogenic Romberg’s’ test described by Lempert et al2 —improved standing balance when distracted. Previous reports have noted repeated buckling of the knees, as seen in case 2, as a feature of functional gait disorders.2 Posturography with and without distraction may be a useful adjunctive investigation in centres where this is available.9

Many bizarre gait and balance problems can accompany in organic disease. For example, patients with treatment-related dyskinesias of Parkinson’s disease may present with symptoms, such as greater ability to walk backwards than forwards.10 Stiff-person syndrome, generalised dystonia, chorea, hydrocephalus and disorders with isolated proprioceptive loss may present with unusual gait, sometimes with normal examination on the bed. Patients with vestibular pathology may also sometimes find they can run better than they can walk.11 Additionally, always bear in mind the possibility that your patient has a functional gait disorder and a ‘neurological’ disease. Factitious gait and balance disorders should remain on the differential diagnosis, but require evidence of marked discrepancy between reported and observed function (not discrepancy in the gait itself); such evidence is hard to obtain.

In our patients, a careful, supportive explanation of the diagnosis of functional gait disorder, including explicit discussion of the positive signs, appeared to assist in treatment.8 There is emerging evidence of the important role of physiotherapy in treating patients with functional gait disorder,12 including a recent positive randomised controlled trial of 60 patients.13 Physiotherapy is also a good setting in which to reinforce the basis of the diagnosis and use clinical features, such as resolution of symptoms with iPhone use, as a positive part of rehabilitation, rather than as a ‘trick’ to catch the patient out.14