Table 1
Neurophysiological Findings in Cases of Acute PHM
| Reference | Findings | Outcome |
|---|---|---|
| Baldy-Moulinier et al.60 | EEG demonstrated bilaterally synchronous spikes and wave. | Patient survived and developed short term memory loss. |
| Madison and Niedermeyer61 | Case 1: continuous generalized synchronous multiple spikes and spike wave like discharges associated with myoclonic jerks. Case 2: continuous rhythmic 2 to 3 per second with a definite spike component. Case 3: generalized synchronous sharp waves of high voltage and a small number associated with myoclonus. Case 4: excessive diffuse slow activity. Case 5: high voltage delta activity; no spikes were noticed. | Cases 1 and 2 survived while the other three patients died. |
| Van Woert et al.62 | EEG: diffuse slowing and occasional theta activity. | This patient survived and went on to develop LAS. |
| Wolf63 | Myoclonus was associated with EEG bursts. | None of the patient survived post-anoxic myoclonus. |
| Niedermeyer et al.64 | Spike activity on EEG seen with myoclonus. | Patient did not regain consciousness and died. |
| Jumao-as et al.11 | EEG performed in 15 patients with anoxic encephalopathy showed burst suppression and generalized periodic complexes as the most common pattern. | None of the patients regained consciousness and all died. |
| Young et al.5 | EEG performed in 6 patients with generalized myoclonus after CPR: burst suppression and alpha coma was commonly seen. | None of the patients with generalized myoclonus after CPR regained consciousness. |
| Harper et al.65 | EEG showed occasional bursts of activity at 7–11 Hz. | Patient survived and developed LAS. |
| Wijdicks et al.14 | Common EEG pattern seen in cases of generalized myoclonus after CPR included burst suppression, polyspiked waves, and alpha coma. | None of the patients with generalized myoclonus after CPR regained consciousness. |
| Wijdicks66 | EEG: burst suppression pattern in 2 patients after hypoxia. | Both patients died. |
| Zivkovic and Brenner67 | No changes in EEG with myoclonus. Tactile stimulation led to generalized spike and wave discharges and generalized myoclonus. | Patient did not regain consciousness and died. |
| Hui et al.68 | EEG was performed in 10 patients who developed generalized myoclonus after anoxia; 6 patients had generalized polyspikes related to myoclonus while other 4 had low voltage diffuse activity. | 16 out of 18 patients with generalized myoclonus died while 1 remained in a persistent vegetative state and another one developed LAS. |
| Thömke et al.69 | Different patterns of EEG were described: burst suppression, continuous generalized epileptiform discharges, and alpha coma. | 45 patients with generalized myoclonus after CPR died while 5 remained in a permanent vegetative state. |
| Fernández-Torre et al.70 | EEG showed burst suppression pattern. Generalized spike and wave discharges were precipitated with touch. | Patient did not regain consciousness and died. |
| Kakisaka et al.26 | EEG: burst suppression pattern.EMG: agonist and antagonist muscle contract simultaneously. | Patient survived with significant disabilities. |
| Fernández-Torre et al.8 | EEG: periodic, regular, generalized burst of slow waves intermixed with prominent spikes, polyspikes, and sharp waves. This pattern was accompanied with eye opening movements. | Patient did not regain consciousness and died. |
| Legriel et al.10 | EEG: artifacts associated with jerks. | Patient did not regain consciousness and died. |
| Arpesella et al.56 | EEG: continuous spikes, polyspikes, and slow wave diffuse activity. | Patient survived and developed LAS. |
| English et al.71 | EEG: frequent myoclonic polyspikes were observed. | Patient developed LAS but eventually died of pneumonia. |
| Datta et al.19 | EEG: continuous generalized sharp and slow epileptiform activity disrupted by bursts of generalized polyspikes. This was not associated with myoclonus. | Patient developed LAS but died later due to hemoptysis. |
| Rossetti et al.17 | EEG in two patients with myoclonus showed bilateral, repetitive, and diffuse sharp waves; third patient: demonstrated sharp, spike waves with stimulus induced rhythmic, periodic, or ictal discharges. All three patients had preserved N20 on SEP. Five patients with axial myoclonus without corresponding EEG changes died.23 patients with myoclonus demonstrated ictal EEG. Only one patient survived out of 23. | 2 out of 3 patients who survived cardiac arrest went on to develop LAS. They were treated with therapeutic hypothermia. |
| Thömke et al.31 | EEG: burst suppression pattern in 39 out of 60 patients and continuous generalized epileptiform discharges in the rest. | 59 patients died and one survived in a persistent vegetative state. |
| Rajamani et al.13 | EEG: generalized periodic discharges with no perceptible background rhythm. | Patient did not regain consciousness and died. |
| Lee and Lee41 | EEG: complex spike waves bifrontally. | Patient developed LAS. |
| Bouwes et al.25 | 3 out of 51 SEPs were giant; EEG: epileptiform activity (33%); status epilepticus (22%); generalized periodic discharges (25%); burst suppression (6%) | Good outcome was observed in 12% of the patients with acute PHM. Only one patient with status myoclonus survived and made a good recovery. |
| Lucas et al.21 | Case 1: EEG: diffusely slow background; Case 2: EEG: burst suppression pattern followed by intermittent epileptiform activity; Case 3: EEG: slow and disorganized background rhythm. | All three patients survived following treatment with therapeutic hypothermia (one patient later died of septic shock). |
| Legriel et al.72 | EEG: burst suppression. | Patient did not regain consciousness and died. |
| Fernández-Torre et al.73 | EEG: burst suppression. | Patient did not regain consciousness and died. |
| Shin et al.74 | EEG: cyclic epileptiform waves. | Patient survived and developed LAS. |
| Mader et al.75 | EEG: spike and wave activity. | Patient did not regain consciousness and died. |
| Accardo et al.20 | Unreactive EEG with diffuse epileptiform discharges associated with continuous generalized multifocal myoclonus. | Patient developed LAS. |
| Tsai et al.76 | EEG showed diffuse cortical dysfunction | Myoclonus was observed after the discontinuation of muscle relaxant which was done for therapeutic hypothermia. Patient regained consciousness after 13th day of cardiac arrest. |
| van Zijl et al.12 | EEG in generalized myoclonus group revealed status epilepticus (64%), diffuse slowing (17%), and burst suppression (11%). Multifocal myoclonus group had diffuse slowing (52%), low voltage (13%), and status epilepticus (13%). | Only 1 patient out of 17 with generalized myoclonus survived. 3 patients out of 43 with PHM developed LAS.34 patients out of 43 with PHM died. |
| Seder et al.16 | EEG: 27% electrographic status epilepticus; 55% epileptiform activity (electrographic seizure or periodic epileptiform discharges) | Good outcome in patients when myoclonus was not associated with epileptiform activity on EEG. |
| Dericioglu et al.9 | EEG: generalized high-amplitude, spike and sharp wave complexes. Around 50 hours after arrest, EEG showed bilateral independent discharges. | Patient did not regain consciousness and died. |
| Sanna et al.77 | Alpha coma pattern was seen on EEG. | Progressed to develop LAS. |
| Walsh BH et al.78 | EEG showed suppressed background with intermittent rhythmic pattern which was later observed to be an artifact. | Patient did not regain consciousness and died. |
Figure 1
Neurophysiological findings in acute PHM. More than one pattern of electroencephalography was seen in the same patient during the course of myoclonus. Burst suppression was the most common pattern while alpha coma was the least common pattern observed. The highest rate of survival was seen in the diffuse slowing group and the lowest rate was seen in the spike-wave group. Multiple studies were commonly performed in the same patient.
Table 2
Neurophysiological Findings in Cases of LAS
| Reference | EEG | EMG | Jerk-locked Back-averaging | Long Latency Reflex | SEP |
|---|---|---|---|---|---|
| Lance and Adams2 | Case 1: spike discharges at paracentral electrode. Case 2: no abnormality. Case 3: atypical spike and wave at 2.5–5 per second. | Spike was usually recorded in all muscles of the limb; contraction was stronger in flexors. | Myoclonic jerks followed shortly after spikes; duration of negative cortical spike varied from 15–35 ms and followed by positive deflection of 10–15 ms. | NA | NA |
| Erbslöh and Prüll79 | 2–4 c/sec spike and wave; polyspike and wave synchronous with the myoclonus. | NA | After a latency of 20–50 ms following the cortical spikes myoclonus was observed. | NA | NA |
| Hirose et al.80 | Bitemporal independent random low amplitude delta slowing. No cortical spike potentials were observed. | NA | NA | NA | NA |
| Tassinari et al.81 | Well-preserved background activity with rare bursts of low voltage sharp theta activity. During REM sleep, typical long lasting bursts of fast spikes over the midline and frontocentral regions. | NA | NA | NA | NA |
| Van Woert et al.62 | Case 1: moderate generalized slow activity with occasional sharp waves. | NA | NA | NA | NA |
| Goldberb and Dorman48 | Case 1: mild slowing. Case 2: focal spikes. Case 3: normal. | NA | NA | NA | NA |
| De Léan et al.43 | Case 1: Muscle artifact; no spike activity observed. Case 2: slow activity over the left hemisphere; no spike activity. | NA | NA | NA | NA |
| Hallett et al.28 | Slow and fast activity over both hemispheres and very frequent spikes followed by slow waves. | The duration of EMG was 10-30 msec. Cranial nerve nuclei were activated in ascending order and arm muscles before the leg. | EEG spikes were not time locked to EMG discharges. | NA | Normal. |
| Carroll and Walsh82 | Central intermittent single and short duration multiple spike and slow wave complexes. Background activity was 6–7 Hz theta activity. Some discharges were associated with myoclonus. | NA | NA | NA | NA |
| Hallett et al.83 | Diffusely slow with mixed sharp waves. | Simple waveform lasting 10 to 30 msec. Cranial muscles activated before the arm and arm muscles before the leg. | An EEG negative transient preceded and was time locked to the myoclonus. | NA | Giant SEPs. |
| Fahn84 | Case 1: generalized spike and slow wave complexes that were maximum parasagittally. Case 2: generalized spike and slow wave complexes that were maximal in frontocentral region. Case 3: fast activity in the frontocentral region. | Case 1: bilaterally symmetrical motor unit discharges that were synchronous in all extremities. Case 2: synchronous contraction in all muscle groups tested. There was no correlation between myoclonic jerks and epileptiform discharges. | NA | NA | Case 1: normal Case 2: normal Case 3: high amplitude waves |
| DeLisa et al.85 | Normal | NA | NA | NA | NA |
| Bruni et al.47 | Frequent bisynchronous spike and polyspike and wave localized to centroparietal region. No relationship was observed between EEG and myoclonus. | NA | NA | NA | NA |
| Rollinson and Gilligan86 | Normal | NA | NA | NA | NA |
| Coletti et al.87 | Paroxysms of symmetrical sharp waves of large amplitude and bursts of polyspike and spike-wave over the central regions. | Demonstrated simultaneous involvement of agonist and antagonist muscles. | Simultaneous EEG–EMG recording did not demonstrate correlation between myoclonus and EEG. | NA | NA |
| Kelly et al.88 | Normal | NA | NA | Normal | Normal |
| Sotaniemi89 | Symmetric slowing and intermittent delta activity. | NA | NA | NA | NA |
| Magnussen et al.90 | Case 1: normal when myoclonus appears. Case 2: 4–6 Hz activity without changes related to the myoclonus. | NA | NA | NA | NA |
| Obeso et al.91 | Excess of generalized theta activity. | Duration of EMG discharge was 60 to 120 msec. | EEG potential was not time locked to the jerk. | NA | Not enlarged. |
| Chee and Poh92 | 5–6 cps theta activity. No epileptiform activity detected. | NA | NA | NA | NA |
| Fahn33 | Case 5: EEG slow background with low voltage spikes and polyspikes bilaterally. | Case 1: EMG shows synchronous and asynchronous firing of leg flexors and extensors. | Case 5: jerk-locked averaging failed to show cortical spikes. | NA | Case 5: normal. Case 6: normal. |
| Hauw et al.36 | Case 1: EEG showed spontaneous paroxysmal crises with spike activity associated with myoclonus. Case 2: EEG showed bilateral delta waves and no spike activity. Case 3: EEG did not show spike associated with myoclonus. Case 4: EEG showed slow waves of 4–5 Hz with intermittent paroxysmal potentials. | NA | NA | NA | NA |
| Kim et al.93 | Slow theta to delta waves were seen in both hemispheres. | NA | NA | NA | Normal. |
| Giménez-Roldán et al.45 | 4–6 Hz bitemporal runs; no activity with myoclonus observed. | NA | NA | NA | NA |
| Witte et al.94 | Spike activity at the vertex when patient performed any movement. | Simultaneous EEG–EMG showed that spikes were present before any myoclonic movement was observed. | NA | NA | Normal. |
| Obeso et al.95 | NA | EMG discharges were brief (less than 50 ms). | NA | NA | Enlarged. |
| Brown et al.30 | Generalized and polyphasic spikes followed by slow wave. The spikes were usually associated with myoclonus. | EMG activity lasting 25–100 ms. | Positive peak preceded the jerk by 10 ms. | NA | Disorganized and of small amplitude. |
| Rizvi and Karetzky96 | Normal | NA | NA | NA | NA |
| Wicklein and Schwendemann97 | Spike and wave activity variably related to the myoclonus. | NA | NA | NA | NA |
| Yamaoka et al.98 | Case 1: spike discharge. Case 2: alpha and theta waves and no spike discharge was seen. | NA | NA | NA | NA |
| Werhahn et al.99 | 7 out of 14 patients with LAS had abnormal EEG. These included: bilateral spikes, sharp waves, polyspike wave complexes sometimes associated with myoclonus. | NA | All patients except one had a time-locked cortical correlate preceding myoclonus. | NA | 2 out of 14 patients with LAS had pathologically enlarged cortical SEPs. One patient had normal SEPs. |
| Lance and Adams, 2001100 | Simultaneous EEG–EMG recording showed spike discharges preceding myoclonus by 7 ms for occipital muscles and 32 ms for quadriceps. | NA | NA | NA | NA |
| Krauss et al.50 | Case 1: several temporal-central spikes. Case 2: generalized slowing but no epileptiform discharges. | NA | NA | NA | NA |
| Frucht et al.38 | NA | NA | Performed in three patients showed cortical origin of myoclonus. | NA | NA |
| Polesin and Stern57 | Spike and polyspike discharges over the vertex region which was consistent with her myoclonic jerks. | NA | NA | NA | NA |
| Zhang et al.40 | Case 1: low amplitude alpha waves, diffuse delta activity, and sharp and slow waves at night. No epileptiform discharge during myoclonus. Case 2: low amplitude theta waves mixed with faster waves; no epileptiform discharge during myoclonus. | NA | NA | NA | NA |
| Datta et al.19 | Sporadic generalized epileptiform discharges not correlated with myoclonic jerks. | NA | NA | NA | NA |
| Arpesella et al.56 | Diffuse alpha activity mixed with theta. | NA | NA | NA | NA |
| Yamada et al.52 | No epileptiform discharges. | Brief generalized bursts lasting 20–30 ms. | NA | NA | Normal. |
| Huang et al.101 | NA | Short duration (<30 ms) myoclonic bursts. | EEG event 26 ms prior to the myoclonus. | NA | NA |
| González de la Aleja et al.58 | Generalized spike and slow wave complexes with mild background slowing. | EEG–EMG simultaneous recording revealed a time locked cortical discharge preceding myoclonus and myoclonus without a correlated EEG. | NA | NA | NA |
| Accardo et al.20 | Normal background with isolated brief polyspike discharges associated with myoclonic jerk. | NA | NA | NA | NA |
| Cho et al.102 | Normal | NA | NA | NA | NA |
| Ferlazzo et al.37 | NA | EEG–EMG simultaneous recording showed generalized spike and polyspike-wave discharges associated with myoclonus. | NA | NA | NA |
| Ilik et al.103 | Frequent myoclonic polyspikes. | NA | NA | NA | NA |
| Budhram et al.104 | Case 1: generalized spike and polyspike wave discharges which correlated with myoclonic jerks. Case 2: no epileptiform activity was observed. | NA | NA | NA | NA |
| Božić et al.105 | Spikes and polyspikes on slow wave background activity. The EEG spikes were highly frequent and generalized. Myoclonus and EEG abnormalities were not linked to each other. | NA | NA | NA | Normal. |
| Asahi et al.51 | NA | Showed a cortical myoclonus pattern. | NA | NA | Normal. |
| Park et al.39 | Frequent bilateral central or hemispheric spike or poly-spike discharges. | NA | NA | NA | NA |
| Sanna et al.77 | Spike and slow wave synchronous with myoclonus. | NA | NA | NA | NA |
