Ciliospinal Reflex

Article Author:
Koushik Tripathy

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Arif Jan

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Tehmina Warsi

2/27/2019 8:54:35 PM


Ciliospinal reflex is characterized by rapid dilation of the ipsilateral[1] pupil (by 1 to 2mm) with a painful or startling stimulus.[2] 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.[3]

Other names of the reflex are[4][5][6][5]:

  • Pupillary skin reflex
  • Cutaneous pupillary reflex
  • Pupillary reflex dilation
  • Pupil dilation response
  • Reflex pupillary dilation
  • Cutaneous pupil reflex or
  • Skin pupillary reflex.

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. 

Issues of Concern

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[7]:

  • Horner syndrome
  • Propofol-induced anesthesia

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 nonreactive pupils) or in pupillometry.[3]  However, the pupil constricts on prolonged exposure (30 to 45 seconds) to light, and there is the preservation of the consensual pupillary response.[3] 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.[3] 

An exaggerated ciliospinal reflex may be present in[8][1]:

  • Asymptomatic patients with a cluster headache - may be due to mechanisms 'proximal to the third order sympathetic neurons'
  • Barbiturate-induced coma - ciliospinal reflex may be present after routine nursing care of critically ill patients

The presence of ciliospinal reflex during and after cardiopulmonary resuscitation may denote a positive prognostic sign for regaining consciousness.[9]

Clinical Significance

Pathway of the sympathetic innervation of the pupil:

The sympathetic efferent pathway has three neurons and is ipsilateral. 

  • The first-order (central) neuron arises from the posterior hypothalamus and descends through the brainstem on the same side close to the trigeminal nucleus. It descends dorsal and rostral to the red nucleus and lies at the lateral tegmentum of midbrain, pons, and medulla. It synapses at the ciliospinal center of Budge, located at C8 to T2 in the intermediolateral (IML) horn of the gray matter of spinal cord.
  • The second-order (preganglionic) neuron originates from the ciliospinal center and goes to the superior cervical ganglion in the neck. It exits the spinal cord through the dorsal spinal root and enters the paravertebral sympathetic chain. The second-order neuron passes near the apex of the lung and may suffer damage in surgeries of the neck or bronchogenic carcinoma (Pancoast tumor) causing Horner's syndrome.
  • The third-order (postganglionic) neuron passes on the surface of the internal carotid artery and joins the ophthalmic nerve at the cavernous sinus. The sympathetic postganglionic fibers pass through nasociliary nerve and long ciliary nerve and reach the ciliary body and the dilator pupillae muscles which are radial muscles of the iris.

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.[1] 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.[10][1] 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 lower cervical spinal cord. However, the noxious stimulus presented to the face registers via the brainstem.[3][10]

Yang and colleagues evaluated the role of the sympathetic nervous system on ciliospinal reflex using topical dapiprazole drops (alpha 1-adrenergic antagonist).[4] 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 suggested supraspinal involvement in the 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.[4] This reflex which is not mediated by the sympathetic fibers is also present in animals and anesthetized humans.[6][11][12]

During recovery after cardiopulmonary resuscitation,[9] pupillary light reflex recovers earlier than ciliospinal reflex. It was suggested 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 leads 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.[6] It was suggested that general anesthesia causes blockade between thalamus and hypothalamus.[6]

The pupillary dilation may correlate with the intensity of pain or stimulus.[13][5]

  • Image 8679 Not availableImage 8679 Not available
    Image courtesy S Bhimji MD
Attributed To: Image courtesy S Bhimji MD

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Ciliospinal Reflex - References


Reeves AG,Posner JB, The ciliospinal response in man. Neurology. 1969 Dec;     [PubMed]
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]
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]
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]
Andrefsky JC,Frank JI,Chyatte D, The ciliospinal reflex in pentobarbital coma. Journal of neurosurgery. 1999 Apr;     [PubMed]
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]
Jørgensen EO, Course of neurological recovery and cerebral prognostic signs during cardio-pulmonary resuscitation. Resuscitation. 1997 Aug;     [PubMed]
Yang LL,Niemann CU,Larson MD, Mechanism of pupillary reflex dilation in awake volunteers and in organ donors. Anesthesiology. 2003 Dec     [PubMed]
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]
LOEWENFELD IE, Mechanisms of reflex dilatation of the pupil; historical review and experimental analysis. Documenta ophthalmologica. Advances in ophthalmology. 1958     [PubMed]
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]
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]
Ellermeier W,Westphal W, Gender differences in pain ratings and pupil reactions to painful pressure stimuli. Pain. 1995 Jun     [PubMed]


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