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PubMed This is a summary of 11 peer-reviewed journal articles Updated
Neurology

Getting the Right Diagnosis: EEGs and MRI

At a Glance

Photosensitive Occipital Lobe Epilepsy (POLE) is diagnosed using two main tests: an EEG with flashing lights to detect specific electrical spikes called a photoparoxysmal response, and an MRI to ensure the brain is structurally healthy. A normal MRI is expected in idiopathic POLE.

The path to a diagnosis for Photosensitive Occipital Lobe Epilepsy (POLE) usually involves two main tools: an EEG to watch the brain’s electrical activity in real-time, and an MRI to look at the brain’s physical structure. Together, these tests help doctors determine if the seizures are a “reflex” to light and whether the brain itself is physically healthy [1][2].

The EEG and Intermittent Photic Stimulation (IPS)

The most important test for diagnosing POLE is an EEG (electroencephalogram) that includes Intermittent Photic Stimulation (IPS) [1].

During this test, the technician uses a strobe light to deliver flashes of light at different speeds, or frequencies, measured in Hertz (Hz) [1]. In individuals with POLE, these flashes can trigger a specific electrical pattern called a Photoparoxysmal Response (PPR) [3].

  • The PPR Pattern: On the EEG monitor, a PPR looks like sudden “spikes” or “sharp waves” of electricity [1].
  • Focal vs. Generalized: In POLE, these spikes often start or are strongest in the occipital region (the back of the brain) [1]. This is different from Generalized Epilepsy, where the spikes usually appear everywhere in the brain at the same time [4].
  • Trigger Frequencies: Most people with photosensitivity are most sensitive to frequencies between 12 and 24 Hz, though every person’s “trigger zone” is unique [5].

Why an MRI is Necessary

While an EEG shows how the brain works, an MRI (Magnetic Resonance Imaging) shows how the brain is built.

In cases of Idiopathic POLE, the MRI is expected to be normal [2][6]. “Idiopathic” means the epilepsy is likely related to genetics or a “natural” state of hyperexcitability rather than a physical injury or scar. Doctors order the MRI primarily to rule out:

  • Cortical Dysplasia: A small area where brain cells didn’t form correctly during development [6].
  • Structural Lesions: Such as tiny scars, tumors, or blood vessel issues that could be irritating the occipital lobe [6].

If the MRI is normal, it provides reassurance that the seizures are likely part of an age-dependent syndrome rather than a structural disease [6].

Differentiating POLE from Similar Syndromes

Because several epilepsy syndromes involve the back of the brain, doctors must distinguish POLE from other conditions:

Syndrome Primary Trigger Main Symptoms
POLE (or IPOE) Light/Patterns [7] Visual hallucinations (colors/flashes) and light sensitivity [8].
Gastaut-Type (COE-G) Spontaneous (No light required) Visual symptoms like POLE, but usually happen without a light trigger [9].
Panayiotopoulos Syndrome Spontaneous (Often during sleep) Autonomic symptoms like intense nausea, vomiting, and paleness [10][11].

By combining the “reflex” triggers found on the EEG with a clean MRI and a clear history of symptoms, your care team can confirm if the diagnosis is POLE and begin a targeted management plan [1][8].

Common questions in this guide

What is a photoparoxysmal response (PPR) on an EEG?
A PPR is a specific electrical pattern of sudden spikes or sharp waves seen on an EEG monitor when the brain is exposed to flashing lights. In POLE, these electrical spikes typically start in the occipital region at the back of the brain.
What does a normal MRI mean if I have POLE?
A normal MRI is expected in cases of idiopathic POLE. It provides reassurance that the brain's physical structure is healthy and the seizures are caused by a natural sensitivity rather than an injury, scar, or tumor.
What frequencies of flashing light trigger POLE seizures?
During an EEG with intermittent photic stimulation, a technician uses a strobe light flashing at different speeds. Most people with photosensitivity are most sensitive to frequencies between 12 and 24 Hertz (Hz), though everyone has a unique trigger zone.
How is POLE different from Panayiotopoulos syndrome?
While both conditions involve the back of the brain, POLE seizures are triggered by light and primarily cause visual hallucinations. Panayiotopoulos syndrome seizures happen spontaneously, often during sleep, and are characterized by intense nausea and vomiting.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.Was the Photoparoxysmal Response (PPR) on the EEG focal (starting in the back of the brain) or generalized (all over)?
  2. 2.At what specific frequencies (Hz) was sensitivity shown during the photic stimulation?
  3. 3.Does the MRI report mention any subtle changes in the 'gray-white matter junction' or any 'cortical dysplasia' in the occipital lobe?
  4. 4.If the MRI is normal, does that confirm the diagnosis of 'idiopathic' POLE?
  5. 5.How do these symptoms specifically differ from Gastaut-type epilepsy or Panayiotopoulos syndrome?

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References

References (11)
  1. 1

    Photoparoxysmal response and its characteristics in a large EEG database using the SCORE system.

    Meritam Larsen P, Wüstenhagen S, Terney D, et al.

    Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology 2021; (132(2)):365-371 doi:10.1016/j.clinph.2020.10.029.

    PMID: 33450559
  2. 2

    Clinical, neuroradiological, and electroencephalographic findings of reflex epilepsies

    Gürsoy G, Tutkavul K, Çetinkaya Y, Tireli H

    Turkish journal of medical sciences 2018; (48(5)):952-955 doi:10.3906/sag-1801-228.

    PMID: 30384559
  3. 3

    Photosensitivity in generalized epilepsies.

    Poleon S, Szaflarski JP

    Epilepsy & behavior : E&B 2017; (68()):225-233 doi:10.1016/j.yebeh.2016.10.040.

    PMID: 28215998
  4. 4

    Symmetry and interhemispheric propagation of paediatric photoparoxysmal response.

    Skadorwa T, Strzelecka J

    Neurologia i neurochirurgia polska 2020; (54(2)):193-199 doi:10.5603/PJNNS.a2020.0030.

    PMID: 32266948
  5. 5

    Are Sub-Saharan epileptic people less photosensitive? A Senegalese study of photoparoxysmal response in a reference epilepsy centre.

    Magnerou AM, Toffa DH, Sow AD, et al.

    Epileptic disorders : international epilepsy journal with videotape 2020; (22(5)):610-622 doi:10.1684/epd.2020.1209.

    PMID: 33146139
  6. 6

    Electroclinical characteristics and syndromic associations of "eye-condition" related visual sensitive epilepsies-A cross-sectional study.

    Karkare KD, Menon RN, Radhakrishnan A, et al.

    Seizure 2018; (58()):62-71 doi:10.1016/j.seizure.2018.03.027.

    PMID: 29665529
  7. 7

    Photo-Dependent Reflex Seizures-A Scoping Review with Proposal of Classification.

    Strzelecka J, Mazurkiewicz DW, Skadorwa T, et al.

    Journal of clinical medicine 2022; (11(13)) doi:10.3390/jcm11133766.

    PMID: 35807051
  8. 8

    Photosensitive occipital lobe epilepsy: Delineation of an under-recognized reflex epilepsy syndrome according to the new ILAE criteria and long-term follow-up.

    Cerrahoğlu Şirin T, Yılmaz T, Elmalı AD, et al.

    Epileptic disorders : international epilepsy journal with videotape 2023; (25(2)):187-199 doi:10.1002/epd2.20011.

    PMID: 36992562
  9. 9

    Clinical dissection of childhood occipital epilepsy of Gastaut and prognostic implication.

    Verrotti A, Laino D, Rinaldi VE, et al.

    European journal of neurology 2016; (23(2)):241-6 doi:10.1111/ene.12840.

    PMID: 26498733
  10. 10

    [Vomiting as a symptom of epilepsy. Panayitopoulos Syndrome - review of the literature and own experience].

    Tworkiewicz M, Sakson-Słomińska A, Kuczyńska R, et al.

    Developmental period medicine 2019; (23(1)):28-33.

    PMID: 30954978
  11. 11

    Self-limited epilepsy with autonomic seizures: A case report.

    Roa JD, Camacho-Cruz J, Pérez-Osorio L, et al.

    SAGE open medical case reports 2023; (11()):2050313X231169573 doi:10.1177/2050313X231169573.

    PMID: 37151738

This page explains diagnostic tests for Photosensitive Occipital Lobe Epilepsy (POLE) for educational purposes only. Always consult your neurologist or epileptologist for specific test result interpretation and medical advice.

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