Pattern sensitivity: a missed part of the diagnosis

Abstract

RationalePattern sensitivity can be diagnosed by presenting a series of visual patterns to the subject in the electroencephalography (EEG) laboratory; however, testing for pattern sensitivity is not routinely done during EEG recording. This work aimed to highlight the incidence of pattern sensitivity among patients referred for routine EEG recording during a 1-year period, identifying the cause of referral, diagnosis, and the characteristics of pattern-sensitive patients.MethodsAll patients aged 4 years and older who were referred for routine EEG during a 12-month period and had no motor or visual impairment were enrolled in the study. Intermittent photic stimulation and pattern sensitivity were tested for each case. Pattern sensitivity was tested by scanning three different rhythmically moving patterns at reading distance with the patient seated in an illuminated room. A pattern evoking a paroxysmal response was reintroduced after exposure to a blank white card to confirm the findings.ResultsTwo hundred twenty-eight patients were studied; twelve patients (5.26%) had pattern sensitivity and their ages ranged from 5 to 12 years. Eight of these patients (66.7%) were referred for seizure disorders, two were referred with the diagnosis of migraine, one with headache and poor scholastic performance and one with recurrent attacks of dizziness for investigation. Seven of the twelve patients (58.3%) had a previous EEG done without testing for pattern sensitivity. Five patients (41.6%) had positive family history for epilepsy, three (25%) for migraine, and two (16.6%) for migraine and epilepsy. Two patients (16.6%) had pattern sensitivity without photosensitivity. Pattern stimulation provoked epileptiform discharges in eight patients (66.6%), focal discharges in one, and unilateral build-up of posterior discharge in three.ConclusionDiagnosis of pattern sensitivity is often missed as it is not routinely tested for during EEG recording. The result of the study challenges the concept of a consistent association between photosensitivity and pattern sensitivity; it also raises questions about the incidence of pattern sensitivity among children who do not suffer from epilepsy and in particular those with migraine, headache and scholastic difficulties. Further studies are therefore needed to clarify the phenotypic spectrum of this EEG trait.

Routine and sleep EEG: Minimum recording standards of the International Federation of Clinical Neurophysiology and the International League Against Epilepsy

“…A PRISMA chart is shown in Appendix S4E. Eighteen observational studies evaluated the use of hyperventilation (Table S12), 24 intermittent photic stimulation (IPS) (Table S13), and nine studies [72][73][74][75][76][77][78][79][80] compared other provocation methods with IPS, hyperventilation, and/or sleep. A proportion of the studies investigated several provocation methods.…”

“…We did not find evidence for supporting the standard use of provocation methods other than hyperventilation and IPS in routine EEG recordings. [72][73][74][75][76][77][78][79][80] Two main indications of other provocation methods were recognized: genetic generalized epilepsies with reflex trait and focal-onset epilepsies with a specific seizure trigger. Three Category III observational studies compared the provocative effect of cognitive tasks to that of sleep deprivation, IPS, and hyperventilation on interictal epileptiform discharges in juvenile myoclonic epilepsy [72][73][74] and two in genetic generalized epilepsies.…”

“…72,73,76 In patients with juvenile myoclonic epilepsy, cognitive tasks were more provocative of myoclonia than conventional methods. 72,73,76 Other Category II-III studies investigated the provocative effect of visual pattern stimulation in unselected patients of 4 to 12 years of age 77 and in pediatric patients with visually induced seizures 78 and olfactory stimuli in mesial temporal lobe epilepsy 79 that did not increase the diagnostic utility of routine EEG.…”

EEG Markers of Treatment Resistance in Idiopathic Generalized Epilepsy: From Standard EEG Findings to Advanced Signal Analysis

“…In addition to intermittent photic stimulation-sensitivity, photosensitive IGE patients may also be reactive to visual patterns, typically stripes. Interestingly, a few pattern-sensitive patients have been described as being unresponsive to conventional intermittent photic stimulation [ 14 ]. In addition, different kinds of cognitive stimuli can trigger seizures in IGE subjects, ranging from verbal (reading, writing, etc.)…”

Visual Evoked Potentials in Rett Syndrome

“…Factors that may weaken the significance of VEP analysis as a biomarker of cortical functioning in RTT include the occurrence of seizures and rarely, pattern-sensitive epilepsy. About 60% of RTT have epilepsy, usually with onset between 3 and 20 years of age [ 2 ], and 5% of children with epilepsy in general may have pattern sensitive seizures [ 3 , 4 ]. Epilepsy, diagnosed in 45% of patients in the above study, was treated with antiepileptic drugs that may have modified VEP responses, but this risk was considered to be small [ 1 ].…”