CAP: A phase (slow+fast), B phase lower amplitude background: Phase A with high proportion of slow wave =
activation/synchrony -likely go to N3/seizure prone; High proportion of fast = deactivation-likely go to N1/wake
(picture Ref 1)
CAPE: Low amplitude fast activities alternate with high amplitude delta - in post concussion with subdural
hematoma case (picture from Ref 2)
Feature NREM Stage N2 CAP (Cyclic Alternating Pattern) CAPE (Cyclic Alternating Pattern
of Encephalopathy)
EEG
Characteristics
Sleep spindles +/- K complex - Phase A: Slow waves ie K-complex
or delta burst followed by faster
activity which is not spindle
- Phase B: Low-voltage background:
Spontaneous or after stimulation-
alternation between the two
patterns in a regular manner for at
least six
Autonomic Stable heart rate/respiration Phase A: Sympathetic dominance
Phase B: Vagal dominance
Cyclic autonomic oscillations (e.g.,
heart rate, respiration) are possible
Appearance Each cycle last 0.5-2 s,
1-2 spindles per 10s
decreasing by age
Each cycle last 2-60s
15-40% of total NREM duration,
increasing by Age
Each cycle 10-60s (ACNS 2021)
Associated
Conditions
Memory consolidation, Sleep
stabilization
CAP Higher >40% -> sleep instability
disorder (NREM parasomnia, OSA,
PLMS, Bruxism)
This may indicate preserved brain
reactivity and recovery potential in
a coma
