What is the difference between tonic and clonic seizure activities in terms of clinical presentation and treatment?

From the Guidelines

Tonic and clonic seizure activities are distinct phases of seizures with different clinical presentations, where tonic seizures involve sustained muscle rigidity and stiffening, and clonic seizures feature rhythmic muscle jerking. The main difference between tonic and clonic seizure activities lies in their clinical presentation and the underlying neurological mechanisms. Tonic seizures are characterized by sustained muscle contraction, fixed posture, and possible loss of consciousness lasting seconds to minutes 1. On the other hand, clonic seizures involve rhythmic muscle jerking with alternating contraction and relaxation of muscle groups, often accompanied by loss of consciousness, possible tongue biting, and incontinence 1.

Key Differences

• Tonic seizures:
  • Sustained muscle rigidity and stiffening
  • Fixed posture
  • Possible loss of consciousness
• Clonic seizures:
  • Rhythmic muscle jerking
  • Alternating contraction and relaxation of muscle groups
  • Often accompanied by loss of consciousness, possible tongue biting, and incontinence Many seizures include both components as tonic-clonic seizures, beginning with the tonic phase followed by clonic movements 1.

Treatment Approaches

Treatment for both types includes antiepileptic medications, and acute management focuses on patient safety by removing hazards, placing the person on their side, and not restraining movements or putting anything in the mouth 1. Status epilepticus (prolonged seizures) requires emergency intervention with benzodiazepines 1.

Clinical Presentation and Treatment

The different presentations reflect distinct neurological mechanisms: tonic seizures result from sustained neuronal firing causing continuous muscle contraction, while clonic seizures involve alternating bursts of neuronal activity and inhibition 1. The treatment approach should prioritize patient safety and timely intervention to prevent complications and improve outcomes.

From the FDA Drug Label

Primary Generalized Tonic-Clonic Seizures During clinical development, the number of patients with primary generalized tonic-clonic epilepsy exposed to levetiracetam was considerably smaller than the number with partial epilepsy, described above.

The difference between tonic and clonic seizure activity is not explicitly described in the provided drug label. However, it mentions Primary Generalized Tonic-Clonic Seizures, which suggests that these are two phases of a seizure.

• Tonic phase is not described.
• Clonic phase is not described. The label does not provide a direct comparison or description of the differences between tonic and clonic seizure activities in terms of clinical presentation and treatment 2.

From the Research

Clinical Presentation of Tonic and Clonic Seizure Activities

• Tonic seizures are characterized by a sudden onset of muscle stiffness, often involving the entire body, and can last from a few seconds to several minutes 3.
• Clonic seizures, on the other hand, are marked by rhythmic muscle contractions and relaxations, typically affecting one part of the body or spreading to other areas 4.
• Generalized tonic-clonic seizures (GTCS) are a type of seizure that combines both tonic and clonic phases, and are considered the most severe form of common epileptic seizure 5.

Treatment of Tonic and Clonic Seizure Activities

• The treatment of tonic and clonic seizures depends on the underlying cause and type of epilepsy, with antiepileptic drugs (AEDs) being the primary treatment option 3.
• Valproate is often considered the first-line treatment for generalized epilepsies, including GTCS, due to its efficacy in controlling seizures 3, 4.
• Other AEDs, such as lamotrigine, levetiracetam, and topiramate, have also been shown to be effective in treating GTCS, and may be considered as alternative or adjunctive treatments 4, 5.
• The choice of AED depends on various factors, including efficacy, adverse effects, interactions, adherence, and mechanism of action, and should be individualized for each patient 5.

Differentiation between Tonic and Clonic Seizure Activities

• The differentiation between tonic and clonic seizures can be challenging, especially in cases where the seizure semiology is not clearly defined 6.
• Semiologic features, such as early head version, figure of four sign, and asymmetric seizure termination, can be useful in differentiating between focal and generalized seizures, but may not be reliable in all cases 6.
• The use of surface electromyography (sEMG) and other objective measures may help improve the accuracy of seizure classification and differentiation between epileptic and psychogenic nonepileptic seizures 7.