Stimulus-Induced Rhythmic, Periodic, or Ictal Discharges (SRIPIDs)

1. STIMULUS-INDUCED RHYTHMIC, PERIODIC, OR ICTAL
DISCHARGES (SIRPIDS)
Ade Wijaya, MD – May
2020

2. INTRODUCTION
- Long term EEG monitoring: observe a patient’s state throughout
various stages of arousal, spontaneous, or otherwise, and in resting
and stimulated states.
- In 2004, Hirsch et al. first described stimulus-induced rhythmic,
periodic, or ictal discharges (SIRPIDs), which reliably elicited by
physical or auditory stimulation.
- The 2013 ACNS criteria provide for the stimulus-induced nature of
rhythmic or periodic patterns to be noted by adding “SI” to a term
that then followed (such as lateralized periodic discharges, LPDs, or
generalized rhythmic delta activity, GRDA) i.e., SI-LPDs or SI-GRDAHirsch LJ, Claassen J, Mayer SA, Emerson RG. Stimulus-induced rhythmic, periodic, or ictal discharges (SIRPIDs): a common EEG phenomenon in the critically ill. Epilepsia 2004;45:109–123.
Hirsch LJ, LaRoche SM, Gaspard N, et al. American clinical neurophysiology society’s standardized critical care EEG terminology. J Clin Neurophysiol 2013;30:1–27.

3. Johnson EL, Kaplan PW, Ritzl EK. Stimulus-induced rhythmic, periodic, or ictal discharges (SIRPIDs). Journal of Clinical Neurophysiology. 2018 May 1;35(3):229-33.

4. Johnson EL, Kaplan PW, Ritzl EK. Stimulus-induced rhythmic, periodic, or ictal discharges (SIRPIDs). Journal of Clinical Neurophysiology. 2018 May 1;35(3):229-33.

5. TYPES AND FOCALITY OF SIRPIDS
- Ictal-appearing discharges to be the most common type of SIRPIDs
(63.6 %)
- Frontal-predominant rhythmic delta activity was the next most
common (42.4 %)
- SI-GPDs (30.3%)
- SI-LPDs (27.3%)
Hirsch LJ, Claassen J, Mayer SA, Emerson RG. Stimulus-induced rhythmic, periodic, or ictal discharges (SIRPIDs): a common EEG phenomenon in the critically ill. Epilepsia 2004;45:109–123.

6. PREVALENCE, SEIZURE
ASSOCIATION, ETIOLOGIES
Johnson EL, Kaplan PW, Ritzl EK. Stimulus-induced rhythmic, periodic, or ictal discharges (SIRPIDs). Journal of Clinical Neurophysiology. 2018 May 1;35(3):229-33.

7. PATHOPHYSIOLOGY
- Activation of thalamic projections to hyperexcitable or
dysfunctional, but not severely injured, cortex
- SIRPIDs were associated with a moderately elevated neuron-specific
enolase level of > 33 ug/L
- May also reflect that SIRPIDs are a transient phenomenon and
resolve with recovery (or deterioration) of the patient’s condition
- Inhibitory GABAA neurotransmission and resulting in hyperexcitable
cortex
Johnson EL, Kaplan PW, Ritzl EK. Stimulus-induced rhythmic, periodic, or ictal discharges (SIRPIDs). Journal of Clinical Neurophysiology. 2018 May 1;35(3):229-33.

8. IMAGING, TREATMENT, OUTCOME
- SPECT : no increase blood flow. Thus, no additional treatment
needed.
- SIRPIDs may reflect a degree of brain injury and have been
associated with more severe illnesses (?)
Zeiler SR, Turtzo LC, Kaplan PW. SPECT–negative SIRPIDs argues against treatment as seizures. J Clin Neurophysiol 2011;28:493–496.
Smith CC, Tatum WO, Gupta V, Pooley RA, Freeman WD. SPECTNegative SIRPIDs. J Clin Neurophysiol 2014;31:e6–e10.
Johnson EL, Kaplan PW, Ritzl EK. Stimulus-induced rhythmic, periodic, or ictal discharges (SIRPIDs). Journal of Clinical Neurophysiology. 2018 May 1;35(3):229-33.

9. SUMMARY
- SIRPIDs are a relatively common finding in continuous EEG
monitoring, commonly seen in patients with traumatic brain injury,
anoxic injury, hemorrhage, or toxicmetabolic disturbances
- Stimulus-induced phenomena, no seizure-related
- Thalamo-cortical projections on abnormal or hyperexcitable cortex
- Treatment of SIRPIDs should follow treatment practices for the
underlying pattern

10. THANK YOU