on 19-Aug-2021 (Thu)

An inguinal hernia (indirect) also occurs through the developmental failure of the processus vaginalis to close. As the testis descends, it pulls a tube of peritoneum along with it. This tube should naturally fibrose and become obliterated but often it fails to fibrose and allows a hernia to form. Recent studies have shown that calcitonin gene-related peptide and hepatocyte growth factor influence the closure of the pro- cessus, raising the possibility of a hormonal cause of hernia development.

The narrowest part of the sac, at the abdominal wall defect, is called the ‘neck of the sac’.

An internal hernia is a term used when adhesions form within the peritoneal cavity. leading to abnormal pockets into which bowel can enter and become trapped. As there is no defect within the abdominal wall, the term ‘hernia’ is confusing.

An abdominal wall hernia has two essential components, a defect in the wall and content, i.e. tissue that has been forced outwards through the defect. The weakness may be entirely in muscle, such as an incisional hernia. It may also be in the fascia, similar to an epigastric hernia through the linea alba. It may have a bony component, such as a femoral hernia. The weakness in the wall is usually the narrowest part of the hernia which expands into the subcutaneous fat outside the muscle. The defect varies in size and may be very small or indeed very large. The nature of the defect is important to understanding the risk of hernia complications. A small defect with rigid walls traps the content and prevents it from freely moving in and out of the defect, increasing the risk of complications

The overlying skin is usually of normal colour. If bruis- ing is present this may suggest venous engorgement of the content. If there is overlying cellulitis then hernia content is strangulating and the case should be treated as an emergency.

In most cases a cough impulse is felt. Gentle pressure is applied to the lump and the patient is asked to cough. If an impulse is felt this is due to increased abdominal pressure being transmitted into the hernia. In cases where the neck is tight and the hernia irreducible there may be no cough impulse. This can lead to failure of diagnosis and is typical of femoral hernia where lack of an impulse leads the clinician to misdiagnose a lymph node.

Histopathology and immunopathology studies reveal inflammation of the artery wall with predominance of CD4+ T lymphocytes and macrophages, which frequently undergo granulomatous organization with formation of giant cells [2]. There is a remarkable loss of vascular smooth muscle cells (VSMC) and elastic fibers that may eventually facilitate aneurysm formation. Inflammation-induced vascular remodeling leads to intimal hyperplasia and lumen occlusion, the source of the ischemic complications of the disease [1,2].

These data strongly suggest that senescence, sex, and genetic background all contribute to the pathogenesis of giant cell arteritis (GCA) [1]. The role of aging and sex remains elusive.

Along with candidate gene studies performed over the years, an international large-scale genotyping effort has confirmed a strong association between GCA and genetic variants in the major histocompatability complex (MHC) region, particularly human leukocyte antigen (HLA)-DRB1*04:04, HLA-DQA1*03:01, and HLA-DQB1*03:02. The derived risk amino acids are located in the antigen-binding pocket of the HLA molecule. These findings support the role of adaptive immunity and the concept that GCA may be an antigen-driven disease [6-8].

The nature of the triggering agent(s) has not been identified with certainty. Periodic increases in incidence observed in some epidemiologic studies suggest a role for environmental factors [9]. Various microbe and viral sequences have been detected in temporal artery lesions, but no convincing causal relationship has been demonstrated [10-14].

The greatest risk factor for developing GCA is aging. The disease almost never occurs before age 50 years, and its incidence rises steadily thereafter, peaking between the ages of 70 to 79 [3], with over 80 percent of patients older than 70 years of age [4,5]. One study found the mean age at incidence of GCA to be 76.7 years [6].

In addition to age, ethnicity is a major risk factor for GCA. The highest incidence figures are found in Scandinavian countries and among Americans of Scandinavian descent.

As with many systemic rheumatic diseases, females are affected more frequently than males, in a ratio of almost 3:1 in populations of Scandinavian descent [3]. The ratio of women to men is lower in Mediterranean countries. Familial aggregation of GCA is not unusual [11].

Polymyalgia rheumatica (PMR) is characterized by aching and morning stiffness about the shoulder and hip girdles, in the neck, and in the torso. PMR is closely linked to giant cell arteritis (GCA), occurring in approximately 40 to 50 percent of patients with GCA [16]. Conversely, GCA is found in approximately 10 percent of patients with PMR.

The precise nature of the relationship between GCA and PMR is not completely understood. In some patients, symptoms and signs of the two conditions occur simultaneously, while in others they appear separately over time.

The pathogenesis of GCA remains poorly understood. One of the mechanisms appears to be the innate pathway in which there is recognition of host cells as foreign by dendritic cells, with activation of the inflammatory cascade, the key mediators being CD4+, IFN-y and IL-6 [1].

As noted above, visual disturbances are important diagnostic symptoms, including visual loss, either partial or complete; amaurosis fugax; double vision and ocular pain. Of these, diplopia occurs rarely and is present in ~5–10% of GCA patients [5], though this is likely underreported due to its transient and retrospective nature, as it was for our patient. Diplopia is associated with higher incidence of permanent visual loss [6].