Infant shuddering syndrome, also known as shuddering attacks or shuddering spells, is a benign condition (meaning unlikely to be harmful) that typically affects babies and young children. It's characterized by brief episodes of rapid shaking or shivering-like movements, usually of the head, shoulders, and sometimes the whole body. These episodes generally last only a few seconds and often occur in clusters throughout the day.
While the incidence of infant shudder syndrome is fairly low, misdiagnosis is fairly common. Naturally, misdiagnosis of this condition can lead to unnecessary treatments and interventions. A misdiagnosed child, for example, can be prescribed anticonvulsant medications (for epilepsy) which can have serious side effects.
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For families with children who were harmed due to misdiagnosis, they can be legally compensated through a medical malpractice claim. Misdiagnosis can cascade into further medical malpractices, such as ordering unnecessary tests, prescribing potentially harmful medications, or failing to treat actual underlying conditions.
Key Takeaways
- Infant shudder syndrome (shuddering attacks) involves brief, involuntary shivering or tremor-like movements of the head, shoulders, and arms, usually lasting only a few seconds.
- Episodes are frequent (sometimes many times per day) but the infant remains fully conscious, alert, and shows no post-episode fatigue, confusion, or drowsiness.
- Unlike seizures, shuddering attacks do not cause loss of awareness, prolonged jerking, or abnormal eye movements, and they do not require antiseizure medication.
- The condition is generally benign and self-limiting, with most children outgrowing it by age 2 to 3 years.
- Possible contributing factors include neurological immaturity, adrenaline surges (from excitement or frustration), low blood sugar, and, in some cases, birth-related stress or minor brain trauma.
Understanding Infant Shudder Syndrome
What Does Baby Shuddering Look Like?
Shuddering episodes in infants typically appear as:
- Sudden, rapid, shiver-like tremors or vibrations, mainly in the head, neck, shoulders, and upper arms, sometimes involving the trunk.
- Brief stiffening or tonic posturing of the neck and upper body, often with facial grimacing (staring, eye deviation, lip tightening, or teeth clenching).
- Movements that resemble shivering but occur when the baby is warm and not cold; they are not triggered by low temperature.
- Episodes that start and stop abruptly during normal activities (such as feeding, diaper changes, or playing) and do not occur during sleep.
- The baby remains awake, aware, and able to interact before, during, and after the episode, with no post-event lethargy or confusion.
Parents often describe it as the baby "shaking something off" or having a quick chill, but video documentation is very helpful for the pediatrician or neurologist to distinguish it from seizures.
How Common Is Infant Shudder Syndrome?
- Shuddering attacks are considered a relatively rare benign paroxysmal nonepileptic event, but they are one of the more common nonepileptic movement disorders in infancy and early childhood.
- In one large pediatric EEG study, shuddering movements accounted for about 7% of all nonepileptic paroxysmal events in children, suggesting they are not extremely rare but often under-recognized.
- Because the episodes can resemble seizures, misdiagnosis is common; many children are initially referred with a suspected seizure disorder before being correctly diagnosed with shuddering attacks.
- The condition is not associated with a specific genetic syndrome or population group and appears to occur sporadically in otherwise healthy infants.
Most experts believe the true incidence is underestimated because many mild cases are never brought to medical attention or are dismissed as "normal baby jitters."
What Causes Infant Shudder Syndrome?
The exact cause of infant shudder syndrome remains unknown, but current understanding points to several possible mechanisms:
- Neurological immaturity: The developing nervous system in infants may produce brief, involuntary muscle movements that resolve as the brain matures.
- Adrenaline surges: Episodes are often triggered by excitement, frustration, or emotional arousal, suggesting a role for autonomic or adrenergic activation.
- Low blood sugar (hypoglycemia): Some studies suggest that shuddering episodes may be more frequent when blood glucose is low, especially in the context of feeding or hunger.
- Birth-related factors: In some cases, a difficult delivery, brief oxygen deprivation (hypoxia), or minor brain trauma may be associated with shuddering-like movements, though this is not the typical cause.
- Possible links to other benign conditions: Shuddering attacks may be a variant of benign myoclonus of early infancy or related to motor tics, but they are distinct from epilepsy and essential tremor.
Importantly, shuddering attacks are not caused by shaken baby syndrome or abusive head trauma; they are a benign, non-epileptic phenomenon when diagnosed correctly.
Infant shudder syndrome typically presents itself between the ages of 4 to 6 months, though they can start as early as a few weeks or up to 18 to 24 months. The onset is usually gradual, with episodes becoming more noticeable over time. Parents often first observe these shuddering spells during times of excitement, while the baby is eating, or during moments of anticipation.
What Are the Signs and Symptoms of Shudder Syndrome?
Shuddering attacks are characterized by:
- Duration: Episodes typically last only a few seconds, usually 4 to 15 seconds, and rarely exceed 15 seconds.
- Frequency: Attacks can occur multiple times per day, ranging from a few episodes to as many as 100 times per day; they may occur in clusters.
- Movement pattern: Rapid shivering or tremor of the head and upper extremities, often with stiffening or tonic posturing of the neck and arms.
- Consciousness: The infant remains fully awake, alert, and responsive during and after the episode, with no loss of awareness.
- Triggers: Episodes are often provoked by excitement, feeding, frustration, or anticipation, and may be aborted if the child is distracted.
- No post-episode symptoms: There is no drowsiness, confusion, weakness, or prolonged abnormal behavior after the attack.
Because the movements can look seizure-like, a neurologist will often recommend video EEG to confirm normal brain activity during an episode and rule out epilepsy.
How Long Does Infant Shudder Syndrome Last?
Shuddering episodes in infant shudder syndrome are typically very brief, lasting only a few seconds and rarely exceeding 15 seconds, though in some cases may occur in clusters of longer intervals. These episodes may occur multiple times a day or every few days; even up to hundreds in some cases.
Most children outgrow infant shudder syndrome by 2 to 3 years of age, and many stop having episodes by age 1 to 2. Occasionally, episodes may persist into early childhood, but this is less common. The frequency and intensity of episodes often fluctuate over time, generally showing a gradual decrease as the child grows older until they stop completely.
Complications That May Arise
As said earlier, infant shuddering syndrome is a generally benign condition. As such, it presents no direct medical complications. Still, families with affected children may still experience anxiety and stress from:
- Unnecessary medical interventions
- Developmental concerns
- Sleep disruptions
- Feeding issues
- Financial strains from testing
With proper education and support, most families navigate this condition without significant long-term issues. Healthcare providers must properly provide sufficient counseling for parents of children with shuddering attacks.
Medical Conditions That Can Be Mistaken for Shuddering
Several medical conditions can be mistaken for shuddering attacks due to similarities in presentation. Given these possibilities, it's crucial for healthcare providers to conduct thorough examinations to ensure accurate diagnosis and appropriate treatment.
Some of these conditions include:
- Epileptic seizures (tonic, myoclonic, or absence seizures)
- Infantile spasms (West syndrome) and other epileptic encephalopathies
- Benign neonatal sleep myoclonus and benign myoclonus of early infancy
- Jitteriness or tremors due to hypoglycemia, hypocalcemia, or withdrawal syndromes
- Tic disorders, such as Tourette's Syndrome
- Stereotypies (repetitive, purposeless movements common in some neurodevelopmental disorders)
- Cerebral palsy or other motor disorders with abnormal movements
- Sandifer syndrome (a rare disorder causing spasmodic torticollis and dystonic body movements)
- Dyskinesias (involuntary muscle movements, sometimes medication-induced)
- Vestibular disorders (can cause brief episodes of dizziness or imbalance)
- Shaken baby syndrome or abusive head trauma (which can cause seizures and abnormal movements)
Misdiagnosing shuddering attacks as other conditions can lead to unnecessary medications that may cause further developmental delays or adverse side effects.
For parents, video recordings of a child's spastic episodes could help medical professionals better identify the condition from which your child is suffering. However, for a more accurate diagnosis, doctors would typically opt for an EEG exam.
Shuddering Attacks vs Seizures: Key Differences
| Feature | Shuddering Attacks (Infant Shudder Syndrome) | Seizures (Epileptic) |
|---|---|---|
| Consciousness | Fully alert and responsive during the episode | Often impaired awareness, blank stare, or unresponsiveness |
| Duration | Very brief (typically 4 to 15 seconds) | Can be brief, but often longer (such as 30 to 60+ seconds) |
| Movement Pattern | Shiver-like tremors of head/arms; may stiffen | Jerking, stiffening, or rhythmic movements; may involve whole body |
| Triggers | Often excitement, feeding, frustration | Often spontaneous; may be triggered by fever, illness, or sleep |
| Post-Episode Behavior | Immediate return to normal; no fatigue or confusion | Often drowsy, confused, weak, or sleepy afterward |
| EEG During Episode | Normal brain waves; only muscle artifacts | Abnormal electrical discharges (spikes, waves) |
| Response to Medication | No benefit from antiseizure drugs | May respond to antiseizure medications |
| Long-Term Risk | Benign; resolves with age; no increased epilepsy risk | May require long-term treatment; risk of recurrent seizures |
Reducing Shudders in Infants
Neurological exams of children with shuddering attacks indicate that they are normal. While there could be some mild developmental delays, most developmental parameters of affected children are generally normal as well.
That being said, parents shouldn't stress about the overall health of their affected kid. Instead, they should look to simply reduce instances of shuddering, ultimately promoting comfort for their kid. Here are some measures parents can take:
- Cultivate a calm environment
- Provide proper nutrition
- Identify and work around the child's triggers
- Maintain a good sleep and eating routine
- Touch and reassurance (during longer or more intense episodes)
- Going to regular medical check-ups
Of course, we still recommend that you reach out to a trusted medical provider for a holistic workaround.
When to Seek Medical Care or a Second Opinion
Parents should seek prompt medical evaluation or a second opinion if:
- Episodes are frequent, prolonged (more than 15 to 20 seconds), or increasing in intensity or frequency.
- The baby loses consciousness, becomes unresponsive, or has abnormal eye movements (such as rolling back or staring).
- There is post-episode drowsiness, confusion, weakness, or difficulty waking up.
- Episodes are associated with developmental delays, regression in milestones, or abnormal muscle tone.
- The child has a history of a difficult birth, oxygen deprivation, or suspected birth injury (such as forceps/vacuum misuse or delayed C-section).
- A doctor diagnoses seizures or prescribes antiseizure medication without clear EEG evidence of epilepsy.
A pediatric neurologist should perform a thorough evaluation, including video EEG, to confirm whether the movements are benign shuddering attacks or a more serious neurological condition.
FAQ
Can Infant Shuddering Be Related to Birth Injury or Misdiagnosis?
Yes, in some cases, infant shuddering can be associated with birth injury or misdiagnosis:
- Birth injury link: Shuddering-like movements may occur after a difficult delivery, especially if there was brief oxygen deprivation (hypoxia), minor brain trauma, or complications like shoulder dystocia. In these cases, the shuddering may be a sign of underlying brain injury (such as mild cerebral palsy) rather than a purely benign shuddering attack.
- Misdiagnosis risk: Because shuddering attacks resemble seizures, they are often misdiagnosed as epilepsy, leading to unnecessary EEGs, MRIs, and antiseizure medications. This can cause significant parental anxiety and financial burden, and may delay recognition of a true birth injury.
- Legal significance: If shuddering episodes are later found to be due to a preventable birth injury (such as failure to monitor fetal distress, improper use of delivery tools, or delayed C-section), families may have a claim for medical negligence and compensation for ongoing care.
What Causes Shudder Syndrome in Infants?
The exact cause is unknown, but likely contributors include:
- Immaturity of the infant's nervous system, leading to brief, involuntary muscle movements.
- Adrenaline surges from excitement, frustration, or emotional arousal.
- Low blood sugar (hypoglycemia), especially around feeding times.
- In some cases, birth-related stress, minor brain trauma, or brief oxygen deprivation during delivery.
- Possible links to benign movement disorders like benign myoclonus of early infancy, but not true epilepsy.
It is important to rule out serious causes (like seizures or brain injury) through proper medical evaluation.
Are Shudder Attacks Linked to Autism?
There is no strong evidence that shuddering attacks themselves cause autism or are a direct sign of autism spectrum disorder (ASD):
- Shuddering attacks are a benign, self-limiting movement disorder and are not considered a core feature of autism.
- However, some children with ASD may exhibit similar "shudder-like" movements as a form of stimming (self-stimulatory behavior) when excited, overwhelmed, or anxious.
- If shuddering episodes are accompanied by other red flags (delayed speech, poor eye contact, repetitive behaviors, or regression), a developmental evaluation for ASD and other neurodevelopmental disorders is warranted.
Shuddering attacks do not mean a child will develop autism, but any concerns about development should be evaluated by a pediatrician or developmental specialist.
Do Babies Grow Out of Shudder Attacks?
Yes, the vast majority of babies grow out of shuddering attacks:
- Shuddering attacks are typically self-limiting and resolve spontaneously with age.
- Most children stop having episodes by age 2 to 3 years, and many outgrow them by age 1 to 2.
- Frequency usually decreases gradually over months, and episodes become less frequent and shorter before disappearing.
- In rare cases, attacks may persist into early childhood, but they do not progress to epilepsy or cause long-term neurological problems when correctly diagnosed as benign shuddering attacks.
If episodes persist beyond age 3 to 4 or are associated with developmental concerns, a neurology follow-up is recommended.
What Age Do Shuddering Attacks Typically Start?
Shuddering attacks usually begin in infancy:
- Onset is most common between 4 and 6 months of age, though they can start as early as a few weeks or up to 18 to 24 months.
- In many cases, the first noticeable episodes occur around the time of teething or increased alertness and interaction with the environment.
- The condition is rare in newborns in the first few weeks and is more typical of older infants and toddlers.
Because onset often coincides with periods of rapid neurological development, early evaluation is important to distinguish benign shuddering from more serious conditions.
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