Stiff Baby Syndrome

A rare neurological disease characterized by the occurrence of hypertonia at birth that progressively decreases over the first year of life. However, attacks of hypertonia heightened by the slightest physical stimulus often occur and are responsible for apnea, respiratory depression, severe cyanosis, and death.

Essential Startle Disease; Exaggerated Startle Reaction; Hyperekplexia Kok Disease; Familial Startle Disease.

First described in 1962 by O. Kok.

Autosomal dominant. There is evidence that the disease is caused by a mutation of the gene for the alpha-1 subunit of the inhibitory glycine receptor on chromosome 5q33.2-5q33.3. The defective receptor causes disruption of the normal inhibitory pathway, descending to the spinal cord to modulate reflexes.

A condition that inhibits the production and release of central gamma-aminobutyric acid (GABA). The pathophysiology of hypertonia and the exaggerated startle response remains unclear but several hypothesis have been proposed. One hypothesis is that there are hyperactive long-loop reflexes acting as the physiologic basis for the startle disease, suggesting increased cortical neuronal excitability. Electroencephalography is normal, whereas electromyography shows persistent muscle activity (even during sleep); rarely associated with electric quietness. The nerve conduction is normal.

The diagnosis is a clinical one and is more easily made when other members of the family are affected. The recognition of this entity is important to avoid an erroneous diagnosis of epilepsy and consequent treatment with anticonvulsants. It is also important to distinguish the stiff baby syndrome from other neurological diseases. Electroencephalography (EEG) and electromyography (EMG) are normal while awake and asleep. Low cerebrospinal fluid (CSF) GABA level was demonstrated. Responsiveness to diazepam and clonazepam therapy.

Onset occurs from birth with hypertonia, hypokinesia, flexed posture, and a peculiar staccato cry. Neonates suffering from the disease are at risk of sudden death from apnea or aspiration if they undergo a prolonged period of rigidity. Later in childhood, individuals may show an exaggerated startle response during waking state with acute generalized hypertonia and loss of voluntary muscle control, resulting in “falling like a log.” The startle can be easily elicited by a loud, unexpected noise or by touching the nose. Marked nocturnal myoclonic jerks are also characteristic. Intelligence is normal. Inguinal/umbilical hernias and congenital dislocation of hip are common. Symptoms are exacerbated by stress, fatigue, cold, and rainy weather.

It is important to mention that affected patients may fall as a consequence of the startle response and injure themselves, i.e., causing bone fractures or even subdural hematomas. Thus, a careful clinical examination and history are recommended prior to an anesthesia to rule out major associated injuries.

No reported experience in the literature although many of these patients had undergone several procedures. In the operating theater, avoid loud noise so as not to produce a hypertonic crisis. Good preoperative communication and premedication may help to allay anxiety. Keep patient warm throughout the perioperative period. Adequate depth of anesthesia and analgesia helps to reduce the perioperative stress. Regional technique is recommended if indicated.

The neuromuscular response to volatile anesthetic agents and succinylcholine might be abnormal; consequently, even if there are no reports of such complications, intraoperative neuromuscular monitoring is recommended. If the patient is on clonazepam, the patient's regular dose should be given on the day of surgery.

In addition to the disorders discussed below, conditions that can produce an increase in muscle tonicity include Encephalomyelitis, Creutzfeldt-Jakob Disease, metoclopramide, strychnine poisoning, and Myoclonic Epilepsy.

Gilles de la Tourette Syndrome: Neurological syndrome characterized by repeated and involuntary stereotyped motor movement (spasmodic twitchings and startling reactions) or vocalization (tics).

Isaacs Mertens Syndrome: Characterized as a peripheral motor neuron disorder leading to muscular stiffness and cramping, particularly in the limbs. Continuous fine vibrating muscle movement (myokymia) can be observed. Muscle relaxation is most often impossible, especially after physical activity. Hypertonia with fasciculations occurs around the age of 30 years; however, neonatal forms have been reported.

Jumping Frenchman of Maine Syndrome: Neurological disease characterized by exaggerated startle reflexes produced by the slightest stimulus. Violent startles associated with echolalia and echopraxia.

Stiff Man Syndrome (Moersch-Wolman Syndrome): Characterized by a neuromuscular condition in which a hyperactive startle reflex results in contraction of muscles causing violent spasms. These spasms are capable of slamming the victim into walls and furniture, causing injuries. An autoimmune disorder has been suggested. Age of onset is around 40 to 50 years.