Ciliospinal reflex is characterized by rapid dilation of the ipsilateral pupil (by 1 to 2mm) with a painful or startling stimulus. It is elicited by scratching or pinching over the skin at the side of the neck, upper trunk, and face. This reflex, which was first described by Budge, is present in normal awake or sleeping humans as well as in comatose patients.
The name denotes the involvement of the ciliary body and the spinal cord. As the mediation of this reflex is by the cervical sympathetic fibers, it is absent in Horner syndrome.
The interplay between the parasympathetic nervous system, which constricts the pupil and the sympathetic nervous system, which dilates the pupil, determines pupillary size.
The ciliospinal reflex is absent in:
The exaggerated ciliospinal reflex may lead to bilaterally dilated pupils which remain dilated for 1 to 6 minutes with minimal or no response to brief exposure to light (seemingly non-reactive pupils) or in pupillometry. However, the pupil constricts on prolonged exposure (30 to 45 seconds) to light, and there is the preservation of the consensual pupillary response. Exaggerated ciliospinal reflex must be ruled out before suspecting non-reactive pupil due to pathologies like increased intracranial tension, third nerve palsy, or midbrain compression in a comatose patient.
The presence of ciliospinal reflex during and after cardiopulmonary resuscitation may denote a positive prognostic sign for regaining consciousness.
Pathway of the sympathetic innervation of the pupil:
The sympathetic efferent pathway has three neurons and is ipsilateral.
Pathway of ciliospinal reflex:
Afferent inputs of this reflex are carried by the trigeminal nerve or cervical pain fibers (lateral spinothalamic tract). The efferent branch of the reflex consists of sympathetic fibers from the upper thoracic and lower cervical spinal cord. The afferent input, when arising from the neck and upper trunk, may activate the second-order sympathetic neurons at the ciliospinal center of Budge bypassing the first order sympathetic neurons or brainstem. Thus, ciliospinal reflex may not be a good indicator of brainstem function or brain death, as the processing of the information may be below the brainstem at or below the level of the lower cervical spinal cord. However, the noxious stimulus presented to the face registers via the brainstem.
Yang and colleagues evaluated the role of the sympathetic nervous system on ciliospinal reflex using topical dapiprazole drops (alpha 1-adrenergic antagonist). They concluded that 'pupillary reflex dilation, as it is clinically performed in awake subjects by stimulating somatic nociceptors, is a sympathetic reflex.' However, the reflex due to the stimulation of somatic nociceptors by high-intensity tetanic electric stimulation is absent in brain-dead organ donors. This presentation suggested supraspinal involvement in pupillary reflex dilation, as if it was a strictly spinal reflex, it would be present in brain-dead individuals who have intact spinal reflexes. However, the brain-dead individuals showed mild pupillary dilation (which was not blocked by dapiprazole) after skin incision. The authors suggested that this dilation was due to inhibition of the pupilloconstrictor nucleus and was not due to a mechanism related to the sympathetic nervous system. This reflex, which is not mediated by the sympathetic fibers, is also present in animals and anesthetized humans.
During recovery after cardiopulmonary resuscitation, pupillary light reflex recovers earlier than the ciliospinal reflex. There has been a suggestion that the central reflexes recover in a caudal to rostral sequence, and thus, the ciliospinal reflex center might be cephalad compared to the pupillary light reflex. Loewenfeld showed that supracollicular decerebration led to the absence of sympathetic-mediated pupillary reflex dilation and hypothesized that the center for sympathetic part of the pupillary reflex dilation is at the thalamus. Some suggest that general anesthesia causes blockade between thalamus and hypothalamus.
During eliciting this reflex, it is always beneficial to have the presence of a nurse who can help with exposing the neck of the patient and can provide the desired level of lighting to examine to pupils.
|||Mullaguri N,Katyal N,Sarwal A,Beary JM,George P,Karthikeyan N,Nattanamai P,Newey CR, Pitfall in Pupillometry: Exaggerated Ciliospinal Reflex in a Patient in Barbiturate Coma Mimicking a Nonreactive Pupil. Cureus. 2017 Dec 30; [PubMed PMID: 29507852]|
|||Reeves AG,Posner JB, The ciliospinal response in man. Neurology. 1969 Dec; [PubMed PMID: 5389693]|
|||Andrefsky JC,Frank JI,Chyatte D, The ciliospinal reflex in pentobarbital coma. Journal of neurosurgery. 1999 Apr; [PubMed PMID: 10193607]|
|||Yang LL,Niemann CU,Larson MD, Mechanism of pupillary reflex dilation in awake volunteers and in organ donors. Anesthesiology. 2003 Dec [PubMed PMID: 14639139]|
|||Chapman CR,Oka S,Bradshaw DH,Jacobson RC,Donaldson GW, Phasic pupil dilation response to noxious stimulation in normal volunteers: relationship to brain evoked potentials and pain report. Psychophysiology. 1999 Jan [PubMed PMID: 10098379]|
|||LOEWENFELD IE, Mechanisms of reflex dilatation of the pupil; historical review and experimental analysis. Documenta ophthalmologica. Advances in ophthalmology. 1958 [PubMed PMID: 13609524]|
|||Ordas-Bandera CM,Sanchez-Marcos C,Janeiro-Lumbreras D,Jimenez-Martin MJ,Muniz-Castrillo S,Cuadrado-Perez ML,Porta-Etessam J, [Neurological examination in patients undergoing sedation with propofol: a descriptive study]. Revista de neurologia. 2014 Jun 16; [PubMed PMID: 24915029]|
|||Havelius U,Heuck M,Milos P,Hindfelt B, The enhanced ciliospinal reflex in asymptomatic patients with cluster headache is due to preganglionic sympathetic mechanisms. Headache. 1997 Sep; [PubMed PMID: 9329232]|
|||Jørgensen EO, Course of neurological recovery and cerebral prognostic signs during cardio-pulmonary resuscitation. Resuscitation. 1997 Aug; [PubMed PMID: 9259054]|
|||Ikeda H,Aruga T,Hayashi M,Miyake Y,Sugimoto K,Mastumoto K, [Two cases in which the presence of ciliospinal response led to indecisiveness in the evaluation of brain death]. No to shinkei = Brain and nerve. 1999 Feb; [PubMed PMID: 10198906]|
|||Larson MD,Sessler DI,Washington DE,Merrifield BR,Hynson JA,McGuire J, Pupillary response to noxious stimulation during isoflurane and propofol anesthesia. Anesthesia and analgesia. 1993 May [PubMed PMID: 8484510]|
|||Larson MD,Tayefeh F,Sessler DI,Daniel M,Noorani M, Sympathetic nervous system does not mediate reflex pupillary dilation during desflurane anesthesia. Anesthesiology. 1996 Oct [PubMed PMID: 8873544]|
|||Ellermeier W,Westphal W, Gender differences in pain ratings and pupil reactions to painful pressure stimuli. Pain. 1995 Jun [PubMed PMID: 7478686]|