Todd's paresis
Encyclopedia
Todd's paresis or Todd's paralysis (or postictal paresis/paralysis, "after seizure") is focal weakness in a part of the body after a seizure
. This weakness typically affects appendage
s and is localized to either the left or right side of the body. It usually subsides completely within 48 hours. Todd's paresis may also affect speech, eye position (gaze), or vision
.
The condition is named after Robert Bentley Todd
(1809-1860), an Irish-born
London
physiologist
who first described the phenomenon in 1849. It may occur in up to 13% of seizure cases. It is most common after generalised tonic-clonic seizures ("grand mal") and may last for hours or occasionally days after the initial seizure. The generally postulated cause is the exhaustion of the primary motor cortex
, although no conclusive evidence is available to support this.
The classic presentation of Todd's paresis is a transient weakness of a hand, arm, or leg after partial seizure activity within that limb. The weakness may range in severity from mild to complete paralysis.
When seizures affect areas other than the motor cortex
, other transient neurological deficits can take place. These include sensory
changes if the sensory cortex
is involved by the seizure, visual field defects if the occipital lobe
is involved, and aphasia
if speech, comprehension or conducting fibres are involved.
Todd's paresis, as defined as any motor deficit after seizure, occurs in 13% of all seizures. This was evaluated in a study of 513 patients with epilepsy with video-electroencephalography
. The same study also showed that the mean duration of postictal paresis was 173 seconds, with ranges of 11 seconds to 22 minutes. There have been case reports of longer durations of paresis, ranging to as long as days.
Other post-ictal neurological findings that do not involve activity of the area affected by the seizure have been described. They are thought to be caused by a different mechanism than Todd's paresis, and including paralysis of the contralateral limb, and rare genetic causes of hemiplegia and seizures.
Todd's paresis is more common after any clonic
seizure activity, and particularly if generalized tonic-clonic seizures occur.
s. Neither has been extensively evaluated.
. The issue is further complicated by the fact that some strokes trigger a focal seizure during the acute phase. A Todd's paresis in this context may overestimate the extent of neurological deficit due to the vascular process itself resulting in erroneous decisions with regards to acute stroke therapy such as thrombolysis
. For this reason a seizure during an acute stroke is generally accepted to be a relative contraindication to thrombolytic therapy, especially in the absence of documented cerebrovascular occlusion using vascular imaging techniques.
An infant with Todd's paresis does not necessarily preclude the diagnosis of a febrile convulsion. This view is as a result of a recent study that showed the incidence of Todd's paresis to be in 0.4% of infants that have been diagnosed with a febrile convulsion.
Seizure
An epileptic seizure, occasionally referred to as a fit, is defined as a transient symptom of "abnormal excessive or synchronous neuronal activity in the brain". The outward effect can be as dramatic as a wild thrashing movement or as mild as a brief loss of awareness...
. This weakness typically affects appendage
Appendage
In invertebrate biology, an appendage is an external body part, or natural prolongation, that protrudes from an organism's body . It is a general term that covers any of the homologous body parts that may extend from a body segment...
s and is localized to either the left or right side of the body. It usually subsides completely within 48 hours. Todd's paresis may also affect speech, eye position (gaze), or vision
Visual perception
Visual perception is the ability to interpret information and surroundings from the effects of visible light reaching the eye. The resulting perception is also known as eyesight, sight, or vision...
.
The condition is named after Robert Bentley Todd
Robert Bentley Todd
Robert Bentley Todd was an Irish-born physician who is best known for describing the condition postictal paralysis in his Lumleian Lectures in 1849 now known as Todd's palsy. He was the younger brother of noted writer and minister James Henthorn Todd.- Early life :He was the son of physician...
(1809-1860), an Irish-born
Ireland
Ireland is an island to the northwest of continental Europe. It is the third-largest island in Europe and the twentieth-largest island on Earth...
London
London
London is the capital city of :England and the :United Kingdom, the largest metropolitan area in the United Kingdom, and the largest urban zone in the European Union by most measures. Located on the River Thames, London has been a major settlement for two millennia, its history going back to its...
physiologist
Physiology
Physiology is the science of the function of living systems. This includes how organisms, organ systems, organs, cells, and bio-molecules carry out the chemical or physical functions that exist in a living system. The highest honor awarded in physiology is the Nobel Prize in Physiology or...
who first described the phenomenon in 1849. It may occur in up to 13% of seizure cases. It is most common after generalised tonic-clonic seizures ("grand mal") and may last for hours or occasionally days after the initial seizure. The generally postulated cause is the exhaustion of the primary motor cortex
Primary motor cortex
The primary motor cortex is a brain region that in humans is located in the posterior portion of the frontal lobe. Itworks in association with pre-motor areas to plan and execute movements. M1 contains large neurons known as Betz cells, which send long axons down the spinal cord to synapse onto...
, although no conclusive evidence is available to support this.
Presentation
When seizures affect areas other than the motor cortex
Motor cortex
Motor cortex is a term that describes regions of the cerebral cortex involved in the planning, control, and execution of voluntary motor functions.-Anatomy of the motor cortex :The motor cortex can be divided into four main parts:...
, other transient neurological deficits can take place. These include sensory
Sensory
Sensory may refer to:relating to senses or smellIn biology:* Sensory preference* Sensory system, part of the nervous system of organisms* Sensory neuron, nerve cell responsible for transmitting information about external stimuli...
changes if the sensory cortex
Sensory cortex
The sensory cortex can refer informally to the primary somatosensory cortex, or it can be used as an umbrella term for the primary and secondary cortices of the different senses : the visual cortex on the occipital lobes, the auditory cortex on the temporal lobes, the primary olfactory cortex on...
is involved by the seizure, visual field defects if the occipital lobe
Occipital lobe
The occipital lobe is the visual processing center of the mammalian brain containing most of the anatomical region of the visual cortex. The primary visual cortex is Brodmann area 17, commonly called V1...
is involved, and aphasia
Aphasia
Aphasia is an impairment of language ability. This class of language disorder ranges from having difficulty remembering words to being completely unable to speak, read, or write....
if speech, comprehension or conducting fibres are involved.
Todd's paresis, as defined as any motor deficit after seizure, occurs in 13% of all seizures. This was evaluated in a study of 513 patients with epilepsy with video-electroencephalography
Electroencephalography
Electroencephalography is the recording of electrical activity along the scalp. EEG measures voltage fluctuations resulting from ionic current flows within the neurons of the brain...
. The same study also showed that the mean duration of postictal paresis was 173 seconds, with ranges of 11 seconds to 22 minutes. There have been case reports of longer durations of paresis, ranging to as long as days.
Other post-ictal neurological findings that do not involve activity of the area affected by the seizure have been described. They are thought to be caused by a different mechanism than Todd's paresis, and including paralysis of the contralateral limb, and rare genetic causes of hemiplegia and seizures.
Todd's paresis is more common after any clonic
Clonus
Clonus is a series of involuntary muscular contractions and relaxations. Clonus is a sign of certain neurological conditions, and is particularly associated with upper motor neuron lesions such as in stroke, multiple sclerosis, spinal cord damage and hepatic encephalopathy...
seizure activity, and particularly if generalized tonic-clonic seizures occur.
Causes
The cause of Todd's paresis is unknown, but there are two hypotheses to its cause. The first is the depletion theory, where the motor cortex is exhausted leading to prolonged neuronal hyperpolarization. The second is that there is transient inactivation of motor fibres caused by activation of NMDA receptorNMDA receptor
The NMDA receptor , a glutamate receptor, is the predominant molecular device for controlling synaptic plasticity and memory function....
s. Neither has been extensively evaluated.
Treatment
Treatment of Todd's paralysis is symptomatic and supportive because the paralysis disappears quickly.Prognosis
An occurrence of Todd's paralysis indicates that a seizure has occurred. The prognosis for the patient depends upon the effects of the seizure, not the occurrence of the paralysis.Importance
The most significant issue regarding the Todd's paresis is its differentiation from a strokeStroke
A stroke, previously known medically as a cerebrovascular accident , is the rapidly developing loss of brain function due to disturbance in the blood supply to the brain. This can be due to ischemia caused by blockage , or a hemorrhage...
. The issue is further complicated by the fact that some strokes trigger a focal seizure during the acute phase. A Todd's paresis in this context may overestimate the extent of neurological deficit due to the vascular process itself resulting in erroneous decisions with regards to acute stroke therapy such as thrombolysis
Thrombolysis
Thrombolysis is the breakdown of blood clots by pharmacological means. It is colloquially referred to as clot busting for this reason...
. For this reason a seizure during an acute stroke is generally accepted to be a relative contraindication to thrombolytic therapy, especially in the absence of documented cerebrovascular occlusion using vascular imaging techniques.
An infant with Todd's paresis does not necessarily preclude the diagnosis of a febrile convulsion. This view is as a result of a recent study that showed the incidence of Todd's paresis to be in 0.4% of infants that have been diagnosed with a febrile convulsion.