Table 2.

Overview of electrophysiological characteristics of the patients with psychogenic PSM, divided into consistent and inconsistent pattern of jerks

Key features polymyography	Consistent pattern (n = 12)	Inconsistent pattern (n = 15)
Burst duration
50–100 ms	1	2
200–500 ms	8	11
>1,000 ms	2	2
Involvement neck/facial muscles (SCM/OO)	2/1	3/1
Variable first muscle	–	15
Synchronicity	5	10
Typical spread	6	2
Conduction
Rapid	5	10
Slow	5	4
Bereitschaftspotential
Present	9	0
Absent	3	5

Burst duration is listed in ms. Consistent jerks were defined as consistent first muscle, topography and/or spread (‘marche’). Rapid conduction was defined as (almost) immediate onset of jerks in non-adjacent muscles

Typical spread rostral and caudal from initial segment/‘marche’, BP Bereitschaftspotential, SCM sternocleidomastoid muscle, OO orbicularis oculi muscle