[MIM 149 400, 614 618, 614 619]

(Stiff baby syndrome, hyperekplexia, Kok disease, Startle disease)

Autosomal dominant or recessive transmission with almost complete penetrance. Behavior characterised by widespread hypertonia at birth and episodes of startle response (with arms spacing and  head retraction) triggered by unexpected auditory or tactile stimuli. This decrease of glycinergic  inhibitors mechanisms is due to mutations

-        in 80 % of cases, of the GLRA1 (5q33.1) or GLRB gene (4q31) coding for the GlyRa1 or GlyRß subunits of the glycine receptor at the level of the reticular pontine substance

-        of the SLC6A5 gene (11p15)(coding for the presynaptic glycine GlyT2 transporter), of the ATAD1 gene (10q23) (coding for the expression of surface AMPA receptors) or the ARHGEF9 genes  (Xq11.1)(coding for collybistine a proteins near the glycine receptor) in the other cases.

The muscle rigidity present at birth decreases progressively during childhood; it is enhanced by minor stimuli (tactile, auditory) or emotions; episodes of jerks (reflex of the newborn consisting of a generalized startle response) caused by a auditory stimulus and followed by a prolonged period of stiffness, that can lead to falls and apneas (especially in case of GLRB or SLC6A5 gene mutation) or aspiration; nerve hyperexcitability; congenital dislocation of the hip ; nocturnal muscle jerks.

Treatment: clonazepam 0.05 to 0.1 mg/kg/day.

The Vigevano’ s maneuver is recommended to stop a hypertonic crisis in infants with apnea: it consists in a forced bending  of the head and limbs on the chest.

Anesthetic implications:

risk of increased stiffness after administration of synthetic opioids or in case of sudden stimuli (noise). Normal response to succinylcholine but abnormal response to the non-depolarizing neuromuscular blocking drugs. One case has been reported of mucular fading during exposure to sevoflurane. No risk of malignant hyperthermia.

References : 

• Murphy C, Shorten G. 
  Train of four fade in a child with stiff baby syndrome. 
  Paediatr Anaesth 2000; 10:567-9.
• Doolittle GM, Greiner AS. 
  Anesthetic complications in an infant with hyperexplexia. 
  Anesthesiology 1990; 73: 181-3.
• Cook WP, Kaplan RF. 
  Neuromuscular blockade in a patient with stiff-baby syndrome. 
  Anesthesiology 1986; 65:525-8
• Eppright B, Mayhew JF. 
  Bilateral inguinal hernia repair in a child with hyperekplexia. 
  Pediatr Anesth 2007 ; 17 : 1099-101.
• Garg R, Ramachandran R, Sharma P. 
  Anaesthetic implications of hyperekplexia –“ startle disease”. 
  Anaesth Intensive Care 2008; 36: 254-6.
• Chau A, Roitfarb M, Carabuena JM, Camann W. 
  Anesthetic management of a parturient with hyperekplexia. 
  A&A Case Reports 2015; 4: 103-6. 
• Chang BA, Bernstein KR.
  Anesthetic management of an adult with hyperekplexia undergoing a laparoscopic colectomy: a case report.
  A&A Practice 2022; 16e01571

Updated: March 2022