🧵1/ What is a somatosensory aura?
A somatosensory aura is an abnormal subjective somatic sensation, involving one or more body parts, typically described as 'tingling' or 'numbness'.
2/ There are three main types of somatosensory auras: Paresthetic auras, Painful auras, Thermal auras
Paresthetic auras are probably the most common type reported by patients.
3/ Paresthetic auras are reported by patients as tingling, numbness or both. These often occur in discrete body parts such as fingers, hand, face etc. and are mostly lateralized. Just like focal clonic seizures, these auras can show a "Jacksonian march".
4/ In one of the largest series ever published on somatosensory auras, the most common sites of these auras were hand & fingers, feet and face.
5/ The symptomatogenic zone of the paresthetic auras is most likely area SI or the primary somatosensory cortex, located in the post-central gyrus (Brodmann area 3b mainly, 1 and 2)
6/ The paresthetic or SI auras, when restricted to limbs, are almost exclusively contralateral. The S1 aura of the face can be bilateral or contralateral but almost never ipsilateral.
7/ The somatotopic map of the SI is well established and it is almost the same as the Penfield motor homunculus.
8/ The other symptomatogenic zone of paresthetic auras is SII or second sensory area, located in the parietal opercular cortex, with it's own distinct homunculus. The presence of this area in cats was first reported by Adrian and Woolsey in the 1940s.
9/ The presence of SII area in humans was first reported by Penfield in 1947 and further elaborated by Penfield and Rasmussen in 1950.
10/ Mazzola, et al. demonstrated that majority of SII stimulations produced paresthetic auras, followed by thermal auras being the second most common. But the SII paresthetic auras are not as discrete as SI auras and the somatotopic organization doesn't follow SI homunculus.
10/ Just like SI, majority of SII limb paresthetic auras are contralateral, but can be bilateral or ipsilateral.
11/ The somatotopic map of SII is relatively well established now since Penfield's original work and has been studied by many investigators. The homunculus is circumscribed and is very condensed. Hand is rostral to face.
12/ Painful and thermal auras are probably the rarest of somatosensory auras. In Penfield & Kristiansen, out of 55 cases with somatosensory auras, only two described these as "cramp-like" pain and four patients described a "thermal" sensation.
13/ In Mauguiere and Courjon's series, pain was the second most common type of somatosensory aura, followed by temperature.
14/ The most likely symptomatogenic zone for painful and thermal auras is the insula or SIII. Majority of stimulation studies have been able to elicit sensations from posterior insula, behind the central sulcus.
15/ Within the posterior insula, from anterior to posterior are- primary & secondary gustatory area, viscerosensitive area, thermal and nociception and general tertiary somatosensory area. @guadalupefbv
16/ Most commonly elicited aura from insular stimulation is still paresthetic, followed by thermal and painful. Most limb sensations are contralateral like SI and SII, but a large percentage of face and trunk sensations are bilateral.
17/ The most common epileptogenic zone associated with somatosensory auras is parietal or peri-rolandic.
18/ SSMA stimulations are also known to produce sensations but these are often bilateral, poorly described and poorly localized.
19/ Conclusions: Most common somatosensory auras are paresthetic, followed by pain and temperature. SI auras are mostly contralateral with discrete localization. SII auras are more widespread and can be bilateral or ipsilateral, but mostly contralateral in limbs.
20/ SIII or insular auras are more likely to be pain and temperature related than SI and SII. The limb SIII auras are mostly contralateral but face and trunk are mostly bilateral and can be ipsilateral. #neurotwitter#epilepsy#seizure#semiology
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🧵1/ What is abdominal (or epigastric) aura?
Abdominal aura is characterized by an uncomfortable sensation in the abdominal region w/wo nausea and w/wo a characteristic 'rising' quality.
2/ In majority of cases, this feeling is localized to the epigastric area, hence the other term 'epigastric aura'. #AurasInEpilepsy #SeizureSemiology
3/ The subjective descriptions of the abdominal aura are quite variable such as 'pain', 'nausea', 'sinking feeling', 'butterflies', 'fluttering', 'fullness', etc. Hence, this aura is mainly defined by the location of the body region affected, rather than type of sensation.
🧵1/ Definition: These are seizures characterized by "twitching" movements of a body part. "Clonus" is simply considered a repetitive form of "Myoclonus"
2/ The "twitch" is produced by a SYNCHRONIZED brief tetanic contraction of both agonist and antagonist muscle groups, followed by SYNCHRONIZED silent periods. This phenomenon is what causes the twitching or the jerking appearance.
🧵1. What is the M2e sign?
The M2e sign is a strong lateralizing sign characterized by an ictal arm movement w/ initial elbow flexion, f/b shoulder abduction & external rotation, with contralateral arm being uninvolved.
2. This peculiar posturing or arm movement may or may not occur with a versive head/eye movement. If it does occur with version, it appears as if the patient is looking at their hand.
3. The phrase "M2e" was coined by C. Ajmone Marsan and B. Ralston in 1957. They used "M2e" as a key formulation to refer to above-defined ictal arm movement in Metrazol-induced seizures.
🧵 What are the cortical zones of epilepsy?
The cortical zone theory of epilepsy postulates the following zones- epileptogenic zone, seizure onset zone, early spread zone, irritative zone, symptomatogenic zone & functional deficit zone. #NeuroTwitter
1/ The epileptogenic zone (EZ) is defined as the minimum area of cortex indispensable for seizure production, which when removed (or disconnected) leads to seizure freedom.
2/ The origins of this concept can be traced back to the 19th century when Sir V. Horsley & JH Jackson planned surgeries for epilepsy patients to remove the so-called "discharging lesion". They only used seizure semiology and macroscopic appearance of lesion to guide resection.
A complex motor sz is a type of motor seizure which is characterized by natural-appearing movements mimicking normal daily life activities e.g. swallowing, lip smacking, gestural etc.
#Neurotwitter #Epilepsy
2/ There are two main subtypes- automotor seizures and hypermotor seizures. Some other rarer forms include gelastic, dacrystic, kissing, spitting, verbalization seizures.
3/ Automotor seizure- This is a type of seizure characterized by mainly distal, natural-appearing organized movements- Oroalimentary, gesticulatory, genital & sexual automatisms.
Dialeptic seizure is defined by a peculiar alteration of consciousness in epilepsy, characterized by complete or partial unresponsiveness w/ motor/behavioral arrest AND amnesia.
#Epilepsy #EEG #SeizureSemiology
2/ The term "dialepsis" was proposed in 1998 to identify and classify this peculiar seizure only by semiology. The term "absence" refers to a subtype of dialeptic seizures which has a characteristic EEG pattern of generalized 3Hz spike and wave (Gen epilepsy).
3/ The term is derived from a Greek verb "διαλειπειν" which means "to interrupt", "stand still" or "pass out".