Getting an Accurate Diagnosis

The diagnosis of Sleep-related hypermotor epilepsy (SHE) is rarely made with a single test. Instead, it is a process of “building a case” based on what you see at home and what specialized tests can reveal ^[1][2]. For many families, the most frustrating part of this process is hearing that a standard test is “normal” when you know something is wrong. Understanding the levels of diagnostic certainty and the limitations of standard tools can help you advocate for the right evaluation.

Why Standard EEGs Often Fail

A routine daytime EEG (electroencephalogram), which records brain waves for 20-30 minutes while you are awake, is frequently uninformative for people with SHE ^[3]. There are several reasons for this:

1. Deep Location: The seizures often start in parts of the brain (like the frontal lobe) that are deep or “hidden” from the sensors placed on the scalp ^[4].
2. Timing: Since these seizures are triggered by sleep, they are unlikely to occur during a brief daytime test ^[1][5].
3. Brevity and Artifact: The events are very brief, and the intense physical movements create muscle artifact (“static”) that can obscure the underlying brain waves. In addition, interictal (between-seizure) abnormalities may simply be absent.

In one study of children with SHE, only about 57% showed abnormal brain waves on their EEG ^[6]. A “normal” EEG does not rule out SHE; it simply means the test did not capture the event or its electrical signature at that moment ^[1][3].

The Three Levels of Certainty

Because testing can be inconclusive, experts use three levels to determine how sure they are of the diagnosis:

• Possible SHE (Witnessed): Based entirely on a doctor taking a clinical history. If the description matches the patterns of SHE—brief, abrupt, and repetitive—it is considered “possible” ^[1].
• Clinical SHE (Video-Documented): This level is reached when you provide a clear video of a typical event. If a neurologist sees the characteristic “hypermotor” movements, the diagnosis becomes much more likely ^[1][7].
• Confirmed SHE (Video-EEG Documented): This generally requires capturing a typical event with appropriate video-EEG/PSG evidence in a hospital or sleep lab ^[1][3].

The Role of Specialized Sleep Studies

To confirm the diagnosis and rule out mimics like night terrors, doctors often use specialized overnight studies.

• Prolonged Video-EEG: Continuous monitoring over one or more nights in an epilepsy unit to capture typical events.
• Video-polysomnography (vPSG): Often used when other sleep disorders are strongly suspected. This adds respiratory, heart rate, and additional sleep-staging sensors to the EEG to track exact sleep stages ^[8][9].

The vPSG looks for probabilistic clues that point toward SHE rather than a common sleep disorder:

• Sleep Stage: Night terrors more commonly happen during N3 (deep sleep). SHE seizures more often occur during N1 or N2 (lighter sleep) ^[10][11].
• Clustering: SHE seizures often happen multiple times in a single night ^[10][12].
• Movement Flow: In SHE, movements usually progress continuously, whereas some parasomnias show a “motor arrest” ^[11]. Note that video-EEG and vPSG can still be nondiagnostic if a typical event is not captured or movement obscures the scalp signal.

Diagnostic Completeness Checklist

To help your care team reach a diagnosis, ensure the following information is gathered and shared:

• [ ] Home Video: Clear footage of a typical event. Prioritize safety: never delay emergency care, do not restrain the person, keep hazards clear, and avoid anything in the mouth. Record only if it can be done from a safe distance without intervention ^[13].
• [ ] Seizure Diary: Log the exact time of each event, how long it lasted, and how many times it happened in one night ^[10].
• [ ] Detailed History: Be ready to describe if the person has a “warning” (aura) before the event or if they are confused afterward ^[1][12].
• [ ] Sleep Staging: If a study is done, ask the doctor if the events occurred during Light Sleep (N1/N2) or Deep Sleep (N3) ^[10].
• [ ] Stereotypy Note: Tell the doctor if the events look like a “carbon copy” of each other every time ^[14].