Definition
The longitudinal fissure, also known as the cerebral longitudinal fissure, is a deep medial groove that separates the left and right cerebral hemispheres of the mammalian brain. It extends from the frontal pole of the cerebrum anteriorly to the occipital pole posteriorly, running roughly along the midline of the skull.
Anatomical features
- Location: Situated on the superior surface of the brain, the fissure lies directly between the two hemispheric cortices.
- Extent: It traverses the entire length of the cerebral hemispheres, from the frontal lobe through the parietal and occipital lobes.
- Surrounding structures: The falx cerebri, a sickle‑shaped fold of dura mater, occupies the interior of the fissure, anchoring to the internal surface of the skull (the tentorium cerebelli) and providing structural support.
- Relation to other fissures: Unlike the lateral sulcus (Sylvian fissure) which separates frontal/parietal from temporal lobes, the longitudinal fissure is the primary midline division of the cerebrum.
Development
During embryogenesis, the telencephalic vesicles proliferate and expand laterally. The longitudinal fissure becomes apparent as the two hemispheric primordia diverge, a process completed by the end of the first trimester in humans. The falx cerebri forms concurrently from mesenchymal tissue derived from the meninges.
Clinical significance
- Neuroimaging: The presence, symmetry, and integrity of the longitudinal fissure are routinely assessed in magnetic resonance imaging (MRI) and computed tomography (CT) scans to evaluate midline shift, which may indicate mass effect from tumors, hemorrhage, or edema.
- Midline shift: A displacement of the fissure greater than 5 mm from its normal central position is considered pathologic and often necessitates urgent intervention.
- Corpus callosum lesions: Because the longitudinal fissure houses the corpus callosum (the main commissural fiber tract), diseases affecting interhemispheric connectivity (e.g., agenesis of the corpus callosum, multiple sclerosis plaques) are evaluated in relation to the fissure’s anatomy.
Comparative anatomy
The longitudinal fissure is present in most placental mammals, reflecting the bilateral organization of the cerebral cortex. In species with less pronounced cortical folding (e.g., rodents), the fissure may be shallower, whereas in highly gyrencephalic animals (e.g., cetaceans) it remains a prominent midline structure.
Etymology
The term combines “longitudinal,” meaning extending lengthwise, with “fissure,” derived from Latin fissura (“a split, crack”). It thus describes a lengthwise split in the brain’s surface.
References
- Standring, S. (2020). Gray’s Anatomy: The Anatomical Basis of Clinical Practice (42nd ed.). Elsevier.
- Purves, D., et al. (2018). Neuroscience (6th ed.). Sinauer Associates.
- Netter, F. H. (2021). Atlas of Human Anatomy (7th ed.). Elsevier.
All information presented reflects established anatomical knowledge as of the current literature.
