What are the clinical features and management of focal tonic seizures?

Clinical Features of Focal Tonic Seizures

Focal tonic seizures are characterized by sustained, asymmetrical posturing of one or more limbs, often without impairment of consciousness, and may be accompanied by voluntary movements in the affected body parts. 1

Clinical Presentation

Motor Manifestations

• Sustained, asymmetrical tonic posturing of one or more limbs is the hallmark feature 2, 1
• Unilateral tonic seizures lateralize to the contralateral hemisphere (opposite side of the brain from the affected limb) 2
• May involve adversive head turning, which is typically contralateral to the epileptic focus 3
• Can occur with preserved awareness, allowing patients to perform voluntary movements during the seizure 1
• Usually brief in duration compared to generalized tonic-clonic seizures 4

Awareness and Consciousness

• Unlike generalized seizures, focal tonic seizures may occur without significant impairment of awareness 5, 1
• Patients may remain fully conscious and able to recall the event afterward 1
• Some patients report being able to perform voluntary movements to alleviate seizure-induced stiffness 1

Associated Features

• May be preceded by focal aware seizures or auras, particularly in parieto-occipital lobe epilepsy (50% vs. 26% in frontal lobe epilepsy) 2
• Can evolve into bilateral tonic-clonic seizures (secondary generalization) in some cases 6
• More commonly seen in extratemporal than temporal lobe epilepsies (79% vs. 1.7%) 2
• Particularly common in frontal lobe epilepsy, where they often occur as the first seizure type in the evolution (67%) 2

Diagnostic Considerations

EEG Findings

• EEG may show focal spikes or ictal activity seconds before clinical onset, often in the frontal midline area for supplementary motor area seizures 1
• Interictal EEGs are typically normal in patients with syncope but abnormal in epilepsy 4
• EEG is crucial for differentiating between focal and generalized seizures 5

Neuroimaging

• MRI is the preferred neuroimaging modality when indicated 5
• May reveal structural abnormalities such as lesions in the medial superior frontal gyrus or supplementary motor area 1
• In many cases, especially with genetic epilepsies, neuroimaging may be normal 1

Differential Diagnosis

Distinguishing from Syncope

• Tonic seizures typically have a more prolonged duration compared to the brief tonic movements sometimes seen in syncope 4
• In syncope, any tonic movements are short (<15 seconds) and start after loss of consciousness, while in seizures, tonic movements often coincide with or precede loss of consciousness 4
• Post-event confusion is usually immediate in syncope but may be prolonged in epilepsy 4

Distinguishing from Non-epileptic Events

• The co-occurrence of tonic posturing with preserved awareness and voluntary movements may lead to misdiagnosis as psychogenic non-epileptic seizures 1
• Careful video-EEG monitoring is essential to confirm the epileptic nature of these events 1

Management Considerations

First Aid

• For any seizure, first aid providers should activate EMS for first-time seizures, seizures lasting >5 minutes, or multiple seizures without return to baseline 4
• First aid providers should minimize injury risk by helping the person to the ground, placing them in recovery position, and clearing the area 4
• First aid providers should stay with the person having a seizure 4

Treatment Approach

• Treatment should be tailored to seizure type and contributing conditions 4
• Patients with 22q11.2 deletion syndrome may benefit from a "start low, go slow" approach to medication dosing due to lowered seizure threshold 4
• Collaboration with epilepsy specialists is recommended for patients with suggestive features 4

Prognosis

• The risk of focal to bilateral tonic-clonic seizure recurrence after treatment initiation is influenced by seizure history and medication management 6, 7
• Approximately 57% of patients with focal to bilateral tonic-clonic seizures do not experience recurrence after treatment initiation 6
• Careful antiepileptic drug management is crucial, as rapid medication reduction is a significant risk factor for seizure generalization 7