What are the clinical features of grand mal seizures in the tonic phase?

Clinical Features of Grand Mal Seizures in the Tonic Phase

The tonic phase of a grand mal seizure is characterized by sustained muscle rigidity, with extension of the limbs, arching of the back, and often a tonic posture that can cause the patient to keel over like a falling log. 1

Key Clinical Features During the Tonic Phase

Body Posture and Movement

• Sustained muscle rigidity with extension of extremities 1
• Tonic posture that often precedes the fall, unlike in syncope where collapse is typically flaccid 1
• Patients may fall stiffly, described as "keeling over like a falling log" 1
• Back arching and neck extension may occur 2

Facial and Ocular Signs

• Eyes typically remain open during the tonic phase 1
• Face may become cyanotic (blue) due to respiratory arrest 1
• Pupillary changes may include dilation or poor responsiveness 1
• Eye deviation may be present as a subtle sign 1

Respiratory Patterns

• Irregular respiratory patterns or temporary cessation of breathing 1
• Initial "ictal cry" may occur at onset due to air being forcefully expelled through partially closed vocal cords 1
• Stertorous (snoring) breathing may develop 1

Duration and Timing

• The tonic phase typically lasts 10-20 seconds before transitioning to the clonic phase 1
• Movements begin at the onset of unconsciousness, unlike in syncope where movements typically start after loss of consciousness 1

Associated Features

Autonomic Changes

• Increased sympathetic activity leading to tachycardia and hypertension 3
• Increased salivation may lead to drooling or frothing at the mouth 1
• Pupillary dilation 1

Neurological Signs

• Complete loss of consciousness coinciding with the onset of tonic movements 1
• No response to external stimuli 3
• Possible tongue biting, typically on the lateral sides of the tongue 1

Distinguishing Features from Other Conditions

• In grand mal seizures, tonic movements begin at the onset of unconsciousness, while in syncope, movements (if present) start after loss of consciousness 1
• Tonic movements in seizures are usually prolonged and symmetrical, unlike the brief, asymmetrical movements seen in syncope 1
• The presence of an "ictal cry" strongly suggests epilepsy rather than syncope or other causes of loss of consciousness 1
• Tongue biting on the lateral side is more indicative of seizures, while tip biting (if it occurs) is more common in syncope 1

Clinical Pitfalls and Caveats

• Subtle or subclinical seizures may manifest only as eye deviation, irregular respiratory patterns, or drooling, making them easy to miss without careful observation 1
• Hypoglycemia may precipitate seizures or posturing and should be considered in cases presenting with seizure-like activity 1
• In the peri-ictal state, pupillary signs and consciousness level may be misleading when assessing for raised intracranial pressure 1
• EEG monitoring is essential for confirming the diagnosis in ambiguous cases, as clinical features alone may sometimes be insufficient 1