SP Ganglion

The sphenopalatine ganglion (SPG), sometimes also called pterygopalatine ganglion, is basically a nerve bundle. More specifically, it is a parasympathetic nerve bundle, which is located in a cavity called pterygopalatine fossa 1 (roughly behind the root of the nose). 

 

Image 1.0: SP ganglion (source: Wikipedia)

So what does the SPG actually do?

First of all, it supplies the lacrimal glands, mucous glands of the nasal cavity, maxillary sinus and palate2. Anatomically, the SPG has three roots1:

  • a parasympathetic root
  • a sympathetic root 
  • a sensory root 

Upon leaving the SPG, all three roots merge to travel through the ptergyopalatine canal, some of them branching further to reach their target organs.

So which role does the SPG play with regard to cluster headache?

Cluster headache is characterised by severe periorbital (i.e. surrounding the orbita) pain which is accompanied by autonomous symptoms (e.g. runny nose, tearing eye, miosis etc.)3. The SPG hosts fibers which supply the lacrimal glands and mucous glands of the nasal cavity, which means that the SPG must be involved in the parasympathetic portion of the autonomous symptoms (runny nose, tearing eye). Also, the SPG lies in close proximity to the maxillary nerve in the pterygopalatine fossa, while also receiving a sensory root from the maxillary nerve2. The latter is a good anatomical explanation for the fact that electrically stimulating the SPG can lead to pain relief in cluster headache3.

 

References:

1. Trepel, M. (2008): Neuroanatomie. Urban & Fischer.

2. Schiebler, T.H., Korf, H.-W. (2007): Anatomie. Steinkopf Verlag.

3. Goadsby, P.J. (2013): Sphenopalatine (pterygopalatine) ganglion stimulation and cluster headache: New hope for ye who enter here. Cephalalgia 0(0) 1–3 .