Tuberculous cervical lymphadenitis

Tuberculous cervical lymphadenitis (also known as Scrofula and King's evil) continues to be seen in endemic areas and in the industrialised world particularly among the immunocompromised. 

Epidemiology

Tuberculous cervical lymphadenitis is the most common manifestation of extra-pulmonary tuberculosis and is a very frequent cause of peripheral lymphadenitis in the developing world. Additionally in industrialised nations there is resurgence among intravenous drug users and the immunocompromised population, especially those due to HIV ^2-3.

Most frequently children and young adults are affected (11 - 30 years of age) and there may be a slight female predilection ².

Clinical presentation

Presentation is usually with one or more cervical masses. Nodes may be hard or fluctuant, but unlike suppurative bacterial lymphadenitis, they tend not be be particularly tender, and only have limited inflammatory changes in the overlying skin ^4-5. If undiagnosed or untreated, spontaneous discharge may eventually occur.

Cervical nodes are the most commonly affected nodes in tuberculous lymphadenitis, accounting for approximately 63% of cases, followed by mediastinal (27%) and axillary nodes (8%) ³. 

Within the neck certain lymph node groups are more frequently involved than others, with a predilection for nodes in the posterior triangle (51%) and deep upper cervical (48%). In the majority of cases lyphadenitis is unilateral ³.

Pathology

Affected nodes demonstrate central caseation, characteristic of mycobacterial infections, which appears as a creamy to chalky off-white regions ³. It is believed that lymphadenitis most likely represent post-primary reactivation of Mycobacterium tuberculosis previously spread haematogeneously during primary infection.

Radiographic features

Imaging alone is often unable to categorically distinguish tuberculous lymphadenitis form other causes of cervical lymphadenopathy and necrotic / cystic lymphadenopathy. It is therefor important to interpret imaging findings with a knowledge of the patients demographics. Interestingly less than 50% of patients with tuberculous cervical lymphadenitis demonstrate abnormalities on chest radiographs ². 

Ultrasound

Ultrasound is an excellent first line investigation, as it is not only able to asses cervical lymphadenopathy but also enables guided fine needle aspiration cytology. The combination of grey-scale imaging and FNAC as a sensitivity of 92% and specificity 97% in distinguishing benign from malignant nodal disease ¹. 

Grey scale features that suggest the diagnosis of tuberculous lymphadenitis above malignancy (the main differential - see below) include:

• nodal matting
• surrounding soft tissue oedema (less marked than one would expect given the size of the collections)

Doppler examination is particularly useful in helping distinguish tuberculous infection from necrotic metastatic disease ¹. Reactive nodes (including those in tuberculous lymphadenitis) demonstrate prominent vascularity, but mostly confined to the hilum, whereas malignant nodes demonstrate more peripheral / capsular vascularity (see US features helpful in distinguishing reactive and malignant lymph nodes).

CT

CT appearances of tuberculous lymphadenitis is variable, depending on the degree of caseation present in the node. Nodes may initially appear merely enlarged, often with attenuation similar to muscle. Eventually central caseation develops and the nodes become centrally low density and eventually frankly cystic. They are usually matted together with only minor surrounding inflammatory changes ⁵.

MRI

MRI appearances are similar to those of CT, ranging form homogeneously enlarged nodes, to cystic transformation with peripheral enhancement.

Treatment and prognosis

Treatment is with prolonged courses of multi-agent antimycobacterials and in some instances (after many months of medical management) surgical excision of residual nodal masses ⁶.

Percutaneous drainage should be avoided prior to medical management as it is liable to create fistulae. 

It is important to note that during therapy new or existing cervical nodes may enlarge. This should not be mistaken for failure of medical management, and such enlargement is often transient ⁶.

Etymology

This condition was known by a number of colourful names:

• Scrofula comes from the Latin for 'brood sow' - exactly what the link is unclear to me.
• King's evil (in the Middle Ages) : it was believed that "royal touch", the touch of the sovereign of England or France, could cure the disease. It is unlikely that this was the case.

Differential diagnosis

Lymph nodes with low density are typically seen with:

• necrotic metastases
  • nasopharyngeal carcinoma : a common differential in asian populations ¹
  • other head and neck squamous cell carcinomas
  • papillary thyroid cancer
• lymphoma : only occasionally have central low density, usually after treatment
• Kimura disease : usually homogeneous enhancing and solid
• Castleman disease
• other infections
  • fungal infection
  • pyogenic infection
  • infectious mononucleosis