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mise à jour du 9 janvier 2003
2001; 56; 1; 138
 Localization of the « sneeze center »
John N. Fink
MBChB, Brookline, MA


The existence of distinct sneeze-evoking centers in the brainstem has been demonstrated in cats, represented bilaterally along the ventromedial spinal trigeminal nuclei and in the adjacent pontomedullary lateral reticular formation. In humans, unilateral damage to the sneeze center in cases of lateral medullary syndrome has resulted in inability to sneeze. The case presented here demonstrates the localization of the sneeze center in humans with more precision.
A 23-year-old woman presented with 10 days of progressive numbness of the face and arms, diplopia, oscillopsia, and dysphagia. She reported an inability to sneeze or yawn and meals were followed by 5 minutes of hiccups. She had a history of venous thrombosis and a family history of systemic lupus erythematosus (SLE). General examination was remarkable for malar rash.
On neurologic examination there was upbeat nystagmus but normal range of eye movement. Left facial sensation was reduced. Facial movementand hearing were normal. Palatal sensation was intact but movement was absent. Cough, swallowing, and tongue movements were impaired. Touch and pin sensation were reduced in the arms but there were no other long-tract signs.
MRI revealed evidence of extensive brainstem demyelination, but no other abnormalities (figure). The diagnosis of SLE was supported by positive ANA and anti-Ro antibodies. CSF was acellular; oligoclonal bands were not present. She was treated with IV methylprednisolone, followed by oral prednisone.
Eight months later her only symptom was persistent inability to sneeze. Nasal irritation resulted in a strong desire to sneeze and she was able to mimic a sneeze voluntarily, but without relief of symptoms. The examination was otherwise normal. Repeat MRI (see the figure) demonstrated a small residual abnormality in the rostral dorsolateral medulla only, where the "sneeze center" has been predicted.
  1. Nonaka S, Unno T, Ohta Y, Mori S Sneeze-evoking region within the brainstem. Brain Res 1990; 511; 265Ð270
  2. Hersch M Loss of ability to sneeze in lateral medullary syndrome. Neurology 2000; 54; 520Ð521
  3. Grant AC, Roter EP Circadian sneezing Neurology 3-1994; 44; 369-375
  4. Suranyi L Localization of the "sneeze center". Neurology 2001; 57(1); 161
To the Editor: Experiments in cats identified a concentration of cells in the rostral dorsolateral pontomedullary area, stimulation of which causes sneezing indistinguishable from sneezing induced by natural peripheral stimuli. The effect of ablation of these cells has not been studied, but in humans one case with a medullary tumor and four cases with lateral medullary syndrome have been described with abortive sneeze reflex (ASR). The inspiratory phase was not followed by the explosive expiratory phase in these individuals, although it could voluntarily be reproduced. All five cases experienced complete recovery of the sneeze reflex within months. The most recent description of a patient with systemic lupus erythmatosus-related demyelination who had ASR with a persisting lesion in the area of sneeze centerl is further evidence that ASR results from a well-defined brainstem lesion.

The subject may, however, be more complex, as the following case illustrates. The patient was a 79-year-old man with sudden onset of right facial weakness and right hemiparesis. Subsequently, he became obtunded and disoriented; his speech output consisted of words, but was inappropriate most of the time. CT scanning showed hernorrhage in the area of left basal ganglia. He improved during the next few days only to deteriorate again into a semivegetative state. During the days he showed improvement, his wife and daughter observed four episodes within an hour that were typical for ASR. In this patient there was no evidence for involvement of the brainstem either clinically or on the CT scan. The fact that patients with ASR can mimic the expiratory phase of sneezing and that it can be voluntarily suppressed in healthy individuals suggests a cortical influence on the sneezing mechanism. It is pure speculation whether interruption of the corticobulbar connections caused ASR in this patient. The important point is that ASR can occur in the absence of a lesion in the sneeze center in the brainstem.

The patient's wife made the interesting comment: "I thought it was normal" So had I until I read Dr. Hersch's report. I have experienced ASR many times and have observed it in family members, friends, and patients. Normal ASR tends ta be sporadic and occurs in the middle of a series of completed sneezes. It is most likely the result of subthreshold. recruitment in the neurons in the pontomedullary sneeze center.

Beyond the scientific value, observations like A.SR serve the purpose of helping clinicians localize abnormalities. Because ASR can be normal or pathologic and the pathologie can be due to a brainstem and or a hemispheric lesion, a more firm statistical connection between ASR and brain lesions has to be established before it can be used for localization purposes. A stroke clinic or an MS center may be the best place ta study and establish such connection. Leslie Suranyi, MD, FRCP(C), Cornwall, Ontario, Canada

Reply from the Authors: I thank Dr. Suranyi for his interest in my report. He correctly points out that the sneeze reflex can be influenced by brain regions above the medulla. The cortical influence on sneezing is recognized by most individuals who can at least partially suppress the reflex voluntarily. In addition, the photic sneeze response is well described and a circadian influence on sneezing has also been suggested.

However, it is difficult to interpret the signs related to Dr. Suranyi by relatives of his patient, who, evidently, was not able to report his own experience. It is possible that the observed sudden inspirations were due to yawning, for example. Even if abortive sneezing is assumed, the observation of several episodes within an hour without obvious external triggers for sneezing might suggest that the basal ganglia hemorrhage resulted in stimulation of the input side of the sneeze reflex, without the threshold for sneeze generation being met.

By contrast, my patient and the previously described patients with medullary lesions all reported the occasional urge ta sneeze in response to normal stimulation and sensation, but were unable to "enjoy" a completed sneeze. These patients were able ta mimic a sneeze voluntarily, however, indicating that despite both input and output comportents of the sneeze reflex being preserved, the sneeze reflex was interrupted by the medullary lesion.

Although Dr. Suranyi's experience indicates that the outward signs suggestive of abortive sneezing might not be specific to lesions in the medulla, the evidence currently available continues to support the model of an integrative sneeze center in the dorsolateral medulla.The sneeze center receives input from sources including the first and second divisions of the trigeminal nerve and higher centers, and triggers a specific, coordinated, all-or nothing motor response when a critical threshold is exceeded. Interaction between the centers on each side must be postulate to explain that the inability to sneeze may result from unilateral lesions involving the sneeze center. From a clinical point of view it is important to note that all of the reported patients with a los of the ability ta sneeze due to a medullary lesion also had othe signs of a brainstern disorder at their first presentation