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
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 ...