Nodding syndrome (NS)
Nodding syndrome (NS) is a neurological condition with unknown etiology. It was first documented in the United Republic of Tanzania (URT) in the 1960s, then later in the Republic of South Sudan in the 1990s and in northern Uganda in 2007. Typically, NS affects children between the ages of 5 and 15 years old, causing progressive cognitive dysfunction, neurological deterioration, stunted growth and a characteristic nodding of the head. Despite numerous and extensive investigations in all three countries, very little is known about the cause of the disease.
To date, Nodding Syndrome is known to occur in the southern region of the United Republic of Tanzania (URT) (Mahenge mountains, Ulanga District), South Sudan (Western Equatoria State, Eastern Equatoria State, Central Equatoria State, and Lakes State) and northern Uganda (Pader, Kitgum and Lamwo districts, with new cases starting to present in Gulu, Amuru, Oyam and Lira districts).
Jilek et al (1962) first described several children with attacks of “head nodding” in Mahenge, a region in URT. The current burden of NS in URT is unknown but observations during case control studies in 2005 and 2009 in the Mahenge region do not suggest a notable increase in the number of cases relative to those detected in the late 1950s and early 1960s.
Samaritan Purse, a local NGO, described observations of head nodding among several children in southern Sudan in the Lui and Amadi villages of East Mundri County in the mid-1990s. A physician from Samaritan Purse reported the outbreak to WHO in 1997. The 2001-2002 investigations by WHO and partners estimated the prevalence of NS at 4.6% among a small population in Western Equatoria State, which appeared to have the highest burden of the illness. By 2003, an estimated 300 cases had been reported from this region. The Ministry of Health of South Sudan estimates the current burden of NS at between six and seven thousand cases, but no systematic large-scale prevalence study has been conducted. The Mundri region in the northeast of Western Equatoria is the presumed epicentre for the disease.
In 2008 and 2009, an illness consistent with NS was reported from Kitgum and Pader Districts in northern Uganda. As of February 2012, Uganda has reported over 3 000 cases of NS from the three districts of Kitgum, Lamwo and Pader. A community survey is underway in Uganda to determine the real burden of NS in the affected districts. Kaiser et al (2009) referred to a phenomenon of head nodding observed in the Kabarole District in Western Uganda as possibly constituting a feature of an epileptic syndrome caused by Onchocerca volvulus (O. volvulus).
The prevalence of both onchocerciasis and epilepsy in the areas affected by NS is high. The affected populations are impoverished and experience regular and prolonged periods of severe food shortages. In South Sudan and in northern Uganda, affected populations have a history of internal displacement and living in internally displaced persons (IDPs) camps.
Familial clustering has been observed in some families with NS patients, with more than one sibling with NS and/or siblings or relatives with other forms of epilepsy.
The age of onset in the vast majority of cases ranges between 5 and 15 years old, but cases have been reported in children as young as 2 years old and in adults up to 32 years old. There is no observed significant difference in the proportion of males to females among the affected, nor is there an observed seasonal variation.