It was agreed that concussion typically involves temporary impairment of neurological function that heals by itself within time, and that neuroimaging normally shows no gross structural changes to the brain as the result of the condition.However, although no structural brain damage occurs according to the classic definition, some researchers have included injuries in which structural damage has occurred and the National Institute for Health and Clinical Excellence definition includes physiological or physical disruption in the brains synapses. Also, by definition, concussion has historically involved a loss of consciousness. However, the definition has evolved over time to include a change in consciousness, such as amnesia, although controversy continues about whether the definition should include only those injuries in which loss of consciousness occurs. This debate resurfaces in some of the best-known concussion grading scales, in which those episodes involving loss of consciousness are graded as being more severe than those without.Definitions of mild traumatic brain injury (mTBI) were inconsistent until the World Health Organizations International Statistical Classification of Diseases and Related Health Problems (ICD-10) provided a consistent, authoritative definition across specialties in 1992. Since then, various organizations such as the American Congress of Rehabilitation Medicine and the American Psychiatric Association in its Diagnostic and Statistical Manual of Mental Disorders have defined mTBI using some combination of loss of consciousness (LOC), post-traumatic amnesia (PTA), and the Glasgow Coma Scale (GCS). Concussion falls under the classification of mild TBI, but it is not clear whether concussion is implied in mild brain injury or mild head injury.
This occurs when the diverticulum inverts into the lumen of the ileum, due to either:An active peristaltic mechanism of the diverticulum that attempts to remove irritating factors
A passive process such as the transit of food

Umbilical anomalies
Anomalies between the diverticulum and umbilicus may include the presence of fibrous cord, cyst, fistula, or sinus, leading to:
Infection or excoriation of periumbilical skin, resulting in a discharging sinus
Recurrent infection and healing of sinus
Abscess formation in the abdominal wall
Fibrous cord increases the risk of volvulus formation and internal herniation

Neoplasm
Tumors in Meckels diverticulum may cause bleeding, acute abdominal pain, gastrointestinal obstruction, perforation or intussusception. Benign tumors:Leiomyoma
Lipoma
Vascular and neuromuscular hamartomaMalignant tumors:Carcinoids: most common, 44%
Mesenchymal tumors: Leiomyosarcoma, peripheral nerve sheath and gastrointestinal stromal tumors, 35%
Adenocarcinoma, 16%
Desmoplastic small round cell tumor

Other complications
A diverticulum inside a Meckels diverticulum (daughter diverticula)
Stones and phytobezoar (a bezoar of vegetable fibers) in Meckels diverticulum
Vesicodiverticular fistula

Pathophysiology
The omphalomesenteric duct (omphaloenteric duct, vitelline duct, or yolk stalk) normally connects the embryonic midgut to the yolk sac ventrally, providing nutrients to the midgut during embryonic development. The vitelline duct narrows progressively and disappears between the 5th and 8th weeks of gestation.In Meckels diverticulum, the proximal part of vitelline duct fails to regress and involute, which remains as a remnant of variable length and location. The solitary diverticulum lies on the antimesenteric border of the ileum (opposite to the mesenteric attachment) and extends into the umbilical cord of the embryo. The left and right vitelline arteries originate from the primitive dorsal aorta, and travel with the vitelline duct.