Obex

Obex
Hind-brain of a human embryo of three months—viewed from behind and partly from left side.
Rhomboid fossa.
Details
Identifiers
Latin	Obex
NeuroNames	636
NeuroLex ID	nlx_151877
TA98	A14.1.04.021 A14.1.05.723
TA2	5982
FMA	78490
Anatomical terms of neuroanatomy [edit on Wikidata]

The obex (from the Latin for barrier) is the point in the human brain at which the fourth ventricle narrows to become the central canal of the spinal cord.

The obex occurs in the caudal medulla.

The decussation of sensory fibers happens at this point.

Clinical significance[]

Lesions at the location can result in obstructive hydrocephalus. The most common lesion at this location is a subependymoma, a benign tumor.^[1] Hemangioblastoma has been observed in this location.^[2] Neurological surgical intervention in the treatment of syringomyelia or hydromyelia may involve plugging the obex to prevent the transmission of cerebrospinal fluid to the central canal of the spinal cord. Gardner suggested plugging of obex with muscle prevents transmission of CSF wave into central canal.^{[clarify][citation needed]}

Detection of prions[]

Immunohistochemistry (IHC) to test brain, lymph, and neuroendocrine tissues for the presence of the abnormal prion protein to diagnose wasting diseases like chronic wasting disease in deer. Positive IHC findings in the obex is considered the gold standard.^[3]

Additional images[]

• 

  Fourth ventricle. Posterior view.Deep dissection.

References[]