Neuroscience Clerkship

 

 
Robert Bentley Todd

 

 

TODD'S PARALYSIS

 

 

Definition:  A temporary weakness or paralysis (typically minutes to hours, rarely days) that occurs in a limb or limbs following a focal or focal-to-generalized seizure.

This phenomenon was first described by an English physician, Robert B Todd (1809 - 1860) (portrait above) who observed the following:

Patients with seizures that began with focal twitching in one body part would then spread over one side of the body (i.e., Jacksonian march) before going on to a generalized tonic clonic seizure. After the seizure, muscles in the limb or the side of the body where the seizure first began would be flaccid and weak.

 

As seizures are a hyperexcitatory state of neurons, the post-ictal state is a depressed state of neuronal function (the neurons have been metabolically stressed and need time to recover). In a generalized seizure, the post-ictal state is also generalized: patients have generalized weakness and a depressed level of alertness.

However, in a focal-onset seizure, presumably the neurons in the focus are the ones most hyperexcitable, and accordingly, in the post-ictal state, the ones most likely to take a greater period of time to recover. In the case of a seizure that originates in the motor cortex, a post-ictal paralysis of the contralateral limb occurs following a seizure.

Although the term Todd’s paralysis was initially used to described hemiparesis after a seizure, there can be other types of post-ictal deficits - it simply depends on whether the seizure had a focal onset and the location of the focus. For example, if the focus is in the primary language area, a patient can have a post-ictal aphasia. Likewise, a focus in the occipital lobe may leave the patient with a post-ictal visual field abnormality.
 
Thus, examining a seizure patient in the immediate post-ictal period is important. Any focal neurologic finding strongly suggest a focal onset. Importantly, in the post-ictal period, it is often not possible to determine if a focal neurologic deficit represents a new neurologic process (e.g., stroke, tumor, etc.) as opposed to a post-ictal deficit. Basically, time will tell.