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Biomedical subjects

T Tylleskär

Publications and source records attributed to T Tylleskär.

At least 19 recordsLinked to original sources
PubMed2004

Neuro-ophthalmological disorders in HIV infected subjects with neurological manifestations.

AIMS: To determine the frequency and features of neuro-ophthalmological manifestations in neurologically symptomatic HIV infected patients and to assess whether or not the visual evoked potential (VEP) features in these patients differ from those of neurologically asymptomatic HIV infected patients. METHODS: Neuro-ophthalmological evaluation was performed in 166 neurologically symptomatic confirmed HIV positive patients, of whom 75 with normal ophthalmological examination were further studied by means of VEPs. The VEPs values were compared to those obtained from 53 other confirmed HIV positive subjects with neither ophthalmological nor neurological manifestations, who served as a comparison group and to the references values of our laboratory. RESULTS: An abnormal neuro-ophthalmological examination was noted in 99/166 patients (60%). Eye movement disorders were present in 99 patients (51%). Visual field defects were detected in 39% of the patients. Optic neuropathy was noted in 31%, papilloedema in 27% and ocular motor nerve palsies in 26% of the patients. Toxoplasmosis and cryptococcosis were the most frequent associated pathologies, though in some patients the HIV itself was the presumed cause. VEPs were abnormal in 57% and 42% of patients with and without neurological manifestations, respectively. Compared to asymptomatic patients, symptomatic patients had a significantly increased mean latency; however, both groups had significant increase in mean latency compared to reference values. CONCLUSION: Neuro-ophthalmological manifestations are common in neurologically symptomatic HIV infected patients. Subclinical dysfunction in the visual pathways is a common phenomenon in both HIV infected patients with and without neurological symptoms, but neurologically symptomatic patients seem to have more damage in their visual pathways.

Adult↗
PubMed2003

Neuro-ophthalmologic findings in konzo, an upper motor neuron disorder in Africa.

PURPOSE: To investigate the neuro-ophthalmological manifestations in konzo, a non-progressive symmetric spastic para/tetraparesis of acute onset associated with consumption of insufficiently processed bitter cassava roots combined with a low protein intake. METHODS: Twenty-one Congolese konzo patients underwent neuro-ophthalmological investigations including visual acuity testing, assessment of light pupillary reflexes, evaluation of ocular motility and deviation, direct ophthalmoscopy, and visual field perimetry. Objective refraction including retinoscopy and keratometry, and slit-lamp biomicroscopy were also done. RESULTS: Five patients had visual impairment, and 14 had temporal pallor of the optic disc. Fourteen presented visual field defects, the most frequent being concentric constriction and peripheral defects. Overall, 11 subjects had symptoms qualifying for the diagnosis of optic neuropathy. Two had spontaneous pendular nystagmus in primary position of gaze. Visual field defects and pallor of the optic discs were found in mild, moderate and severe forms of konzo. No correlation was found between the severity of the motor disability of konzo and the extent of visual field loss. CONCLUSIONS: Konzo was associated with optic neuropathy and a few patients had nystagmus. Although the etiopathogenesis of this optic neuropathy remains to be elucidated, the symmetry of the involvement suggests a toxic origin. We suggest that cyanide causes the neuro-ophthalmological damage in konzo. However, the optic neuropathy in konzo patients does not resemble the features of the epidemic optic neuropathy in Tanzania, Cuba or Nigeria, Leber's hereditary optic neuropathy, tobacco amblyopia or vitamin B deficiency.

Adolescent↗
PubMed2001

Impairments, disabilities and handicap pattern in konzo--a non-progressive spastic para/tetraparesis of acute onset.

PURPOSE: To assess impairments, disabilities and handicap pattern in konzo. METHOD: The study included 17 konzo subjects, of which three were males and 14 females (mean age 21, median 18 years). A detailed neurological examination was performed on all subjects. Subsequently, an assessment of impairments, disabilities and handicap was done with a constructed rating scale partially based on the ICIDH-2 framework. RESULTS: The overall disablement picture in all subjects consisted of motor dysfunction in lower limbs leading to limitations in walking and movement activities, and restrictions in mobility. Hip mobility was severely impaired in most cases (15/17). Although konzo subjects showed normal muscle power in upper limbs (13/17), they had impaired fine motor function (10/17). CONCLUSION: Further studies are needed to assess the effectiveness of the WHO criteria for konzo in defining its forms. The applicability of the ICIDH-2 framework in this study demonstrates the possibility of its use as a common language among researchers in the field of motor disorders. However, a revision is suggested of its taxonomy, and a definition of operational criteria to clarify the content of different qualifiers provided to assess the level of functioning or disability.

Adolescent↗
PubMed2001

High cassava production and low dietary cyanide exposure in mid-west Nigeria.

OBJECTIVE: To investigate if high cassava production levels indicate high consumption and high dietary cyanide exposure in three villages situated within the area of Nigeria with higher cassava production than predicted by a geographic model for cassava production in Africa. DESIGN: Exploratory assessment of: cassava production and processing by qualitative research methods and quantification of residual cyanogens in products; cassava consumption by food frequency and weighed food records and dietary cyanide exposure by urinary thiocyanate and linamarin. SETTING: Rural communities of Afuze, Ebue and Ofabo in mid-west Nigeria. SUBJECTS: 110 subjects from 42 households in three villages for food frequency interviews; 118 subjects in nine Ofabo households for weighed food records. RESULTS: Cassava cultivation was reported to have increased in the preceding 20 years. It was consumed daily by 37 (88%) households, but its mean contribution to daily energy intake was only 13% The range of residual cyanogens in cassava foods was 0 to 62 mg HCN equivalent/kg dry weight (dw). Ten samples (19%) had levels above the 10 mg HCN equivalent/kg dw FAO/WHO safety limit. Mean urinary thiocyanate and linamarin were 51 and 20 micromol/L, indicating low cyanogen intake and dietary cyanide exposure. CONCLUSION: High cassava production levels did not result in high consumption and high dietary cyanide exposure levels, therefore cassava production levels cannot be used to predict consumption or cyanide exposure levels in the study area. A large part of the production is explained by intensive sales.

Adult↗
PubMed2000

Dietary cyanide from insufficiently processed cassava and growth retardation in children in the Democratic Republic of Congo (formerly Zaire).

Dietary cyanide exposure from cyanogenic glucosides in insufficiently processed cassava has been advanced as a contributing factor in child growth retardation. Whether cyanide exposure aggravates children's growth retardation was studied by comparing two populations of children from the northern and the southern zones of the Bandundu region, Democratic Republic of Congo (former Zaire), using dietary interviews, anthropometry and urine analyses. Both populations consumed cassava as their staple diet, but whereas in the north the cassava was well processed, in the south it was inadequately processed. The mean urinary thiocyanate was much higher in the south, whereas mean urinary sulphate excretion was equally low in the two areas. However, the mean urinary SCN/SO4 molar ratio was higher in the south (0.20), indicating that 10-20% of sulphur amino-acids were used for cyanide detoxication. No significant differences were found between the two populations in weight-for-height and weight-for-age indices but the height-for-age index was significantly lower in children from the south, indicating more severe growth retardation in children exposed to dietary cyanide. Because of the preferential use of sulphur amino-acids for cyanide detoxification in the human body, dietary cyanide exposure from cassava may be a factor aggravating growth retardation in Bandundu.

Anthropometry↗
PubMed2000

Low dietary cyanogen exposure from frequent consumption of potentially toxic cassava in Malawi.

In a cassava-growing area in Malawi, where roots are processed by soaking and water is available throughout the year, we interviewed 176 women farmers regarding their preferences for cassava cultivars and frequency of cassava consumption. Dietary cyanogen exposure was estimated from urinary levels of linamarin, the cyanogenic glycoside in cassava, and urinary thiocyanate, the main cyanide metabolite. Protection against unplanned harvest by family members, theft and animal spoilage were stated to be very important reasons for growing bitter cassava cultivars by 91%, 90% and 74% of the women, respectively. The mean (+/- SD) number of cultivars grown by each woman was 4.6 (+/- 2.4). The correlation between mean taste and mean danger scores for the 25 most grown cultivars was strong (r > 0.98). The scoring indicated that cultivars belonged to two distinct groups, eight to a group referred to as 'cool' and 17 to a group termed 'bitter'. The dumpling-like porridge (kondowole) made from cassava flour from bitter roots was eaten twice daily by 51% and at least weekly by 81%. The mean (+/- SEM) urinary linamarin was 14 (+/- 1) mumol/L and thiocyanate was 50 (+/- 4) mumol/L, less than a tenth of levels reported from populations eating insufficiently processed bitter cassava roots, and in the same range as in a non-smoking Swedish reference population. We conclude that cyanogenesis is a preferred characteristic of cassava by the studied farmers because it enhances food security. The availability of water and their knowledge about toxicity and processing enables these women farmers to provide a safe staple food from bitter cassava roots.

Adolescent↗
PubMed1997

Geographical and seasonal association between linamarin and cyanide exposure from cassava and the upper motor neurone disease konzo in former Zaire.

High cyanide intake from consumption of insufficiently processed cassava has been advanced as a possible aetiology of the upper motor neurone disease konzo. However, similar neurodamage has not been associated with cyanide exposure from any other source. With an ecological study design, we compared 22 cases of konzo, 57 unaffected household members and 116 members from unaffected households, a total of 195 subjects, in konzo-affected savanna villages with 103 subjects in adjacent non-affected forest villages in the Paykongila area in the Bandundu Region, Zaire. In the dry season, the mean value (+/- SEM) of urinary thiocyanate, the main cyanide metabolite, was higher in the three groups in konzo-affected villages (563 +/- 105, 587 +/- 44 and 629 +/- 47 micromol/l) than in unaffected villages (241 +/- 17 micromol/l). In affected villages in the dry season when konzo incidence was high, mean urinary thiocyanate was also higher than the levels found in the wet season when incidence was low. The wet season values (mean +/- SEM) were 344 +/- 60, 381 +/- 35 and 351 +/- 27 micromol/l. Urinary levels of inorganic sulphate were low in all groups, indicating low intake of the sulphur amino-acids which provide a substrate for cyanide detoxification. These findings support an aetiological role for cyanide in konzo. However, urinary linamarin, the cyanogenic glucoside and source of cyanide in cassava, was more closely associated with the occurrence of konzo. The mean value (+/- SEM) of urinary linamarin in the konzo cases was 632 +/- 105 micromol/l and in their household members 657 +/- 52 micromol/l, which was significantly higher than in members of control households in the same village (351 +/- 28 micromol/l) and in unaffected villages (147 +/- 18 micromol/l). This suggests that a specific neurotoxic effect of linamarin, rather than the associated general cyanide exposure resulting from glucoside breakdown in the gut, may be the cause of konzo.

Adolescent↗
PubMed1996

Cyanide detoxification in rats exposed to acetonitrile and fed a low protein diet.

Different neurological syndromes have been associated with exposure to cyanide. Dietary cyanide exposure from cassava roots combined with a low intake of the sulfur amino acids necessary for cyanide detoxification has been implicated in the causation of konzo, an upper motoneuron disease identified in Africa. We have investigated the effect of a low protein diet on the capacity for cyanide detoxification. Rats were fed normal chow containing 18% protein or a low protein diet with 5% protein. To expose rats to cyanide the drinking water was supplemented with 40 or 80 mM acetonitrile (CH3CN) for up to 4 weeks. Weight gain was monitored and 24-hr urines were collected for analyses of total sulfur, inorganic sulfate, thiocyanate, and 2-aminothiolazine-4-carboxylic acid (ATC). Blood was collected for analyses of cyanide and cyanate. Rats on a normal diet grew throughout the experiment, while those on a low protein diet initially lost weight and then stabilized at a constant weight. Rats exposed to acetonitrile all progressively lost weight, those on a low protein diet at the highest rate. Signs of neurological damage were not observed. Rats not exposed to acetonitrile excreted < 0.2% of sulfur as thiocyanate and those on a low protein diet reduced their total sulfur excretion to one-third that of rats of the normal diet. Rats on the normal diet did not change total sulfur excretion during exposure to acetonitrile, although thiocyanate now contributed more than two-thirds of excreted sulfur. Rats on a low protein diet exposed to acetonitrile increased both total sulfur and thiocyanate excretion to the levels of rats on a normal diet. Rats exposed to acetonitrile had manyfold increases of circulating concentrations of cyanide and cyanate and of urinary excretion of ATC. There was a positive correlation between blood cyanide concentrations and the plasma concentration of cyanate. It is concluded that the rat has a high capacity for detoxification of cyanide. During adaptation to a low protein intake, sulfur is conserved but cyanide detoxification is still possible at the cost of extensive protein catabolism. It is thus possible that subclinical cyanide exposure could interfere with normal growth and development. The observation of a relationship between circulating cyanide on the one hand and circulating cyanate and urinary excretion of ATC on the other highlights the possibility that cyanide metabolites may mediate neurotoxic effects of cyanide.

Acetonitriles↗
PubMed1995

Dietary determinants of a non-progressive spastic paraparesis (Konzo): a case-referent study in a high incidence area of Zaire.

BACKGROUND: Konzo is an upper motor neuron disease in Africa, characterized by an abrupt onset of a permanent but non-progressive spastic paraparesis. It is named after the local designation in the first report from Zaire. Konzo has been attributed to a metabolic insult from the combined effect of high cyanide and low sulphur intake from several weeks of exclusive consumption of insufficiently processed bitter cassava roots. METHODS: The association between insufficient soaking of cassava roots and konzo is assessed in a matched case-referent study with multivariate conditional logistic regression including 57 case-referent pairs from a rural high incidence community of Zaire. RESULTS: In the multivariate analysis short processing of cassava in the form of only 2 nights soaking yielded an odds ratio of 11.0 (95% confidence interval 1.7-73) when controlling for poverty-related factors and diet. We also show a dose-response relationship for insufficient cassava soaking, both unadjusted and adjusted for potential confounders. CONCLUSIONS: This study supports a causal relationship between insufficient processing of bitter cassava and konzo.

Adolescent↗
PubMed1994

Konzo in the Central African Republic.

We identified a new focus of konzo, an upper motor neuron disease, in a part of western Central African Republic. Interviews and high serum levels of thiocyanate indicate that cyanide exposure from insufficiently processed cassava may cause konzo. Abrupt onset, nonprogressive course, and seronegativity to HTLV-I clearly differentiate konzo from HTLV-I-associated myelopathy in tropical countries.

Adolescent↗
PubMed1993

Konzo: a distinct disease entity with selective upper motor neuron damage.

Two Tanzanian patients with konzo were severely disabled by a non-progressive spastic paraparesis, since the sudden onset during an epidemic six years earlier. At the time of onset they had a high dietary intake of cyanide from exclusive consumption of insufficiently processed bitter cassava roots. MRI of brain and spinal cord were normal but motor evoked potentials on magnetic brain stimulation were absent, even in the only slightly affected upper limbs. Other neurophysiological investigations were largely normal but the more affected patient had central visual field defects. Konzo is a distinct disease entity with selective type upper motor neuron damage.

Adult↗
PubMed1992

Cassava cyanogens and konzo, an upper motoneuron disease found in Africa.

Konzo is a distinct form of tropical myelopathy characterised by abrupt onset of spastic paraparesis. Epidemics in East Africa have been attributed to dietary cyanide exposure from insufficiently processed cassava but a study done in Zaire disputed such an aetiology. We investigated a konzo-affected population in rural Zaire and measured the cyanogen content of cassava flour, determined urinary thiocyanate as an indicator of cyanide intake, and compared blood cyanide concentrations in cases and controls. The affected population consumed flour made from short-soaked (one day) cassava roots and thus had high dietary cyanide exposure (urinary thiocyanate in 31 children = 757 mumol/l) compared with the unaffected population (urinary thiocyanate in 46 children = 50 mumol/l) that ate cassava that had been soaked for three days before consumption. 3 konzo patients, but only 2 of 23 controls, had blood cyanide concentrations above 4 mumol/l (p less than 0.01), although serum thiocyanate concentrations were similar. Our findings indicate a causal role in konzo of sustained high blood cyanide concentrations maintained by a deficient sulphur intake impairing cyanide to thiocyanate conversion. The underlying causes of konzo are poverty and food shortage, but a minor improvement of food processing may, as in beri-beri, be preventive.

Adolescent↗
PubMed1992

[High prevalence of konzo associated with a food shortage crisis in the Bandundu region of zaire].

Konzo is a form of spastic paraparesis reported from several rural areas in Sub-Saharan Africa. It has been attributed to cyanide exposure from exclusive consumption of insufficiently processed bitter cassava roots. We have tested this attribution in a community based epidemiological survey in an area of Bandundu region in Zaire composed of two agro-ecological zones: savanna and forest. In the savanna area with poor soils we found 78 konzo cases in 1,936 inhabitants, a prevalence of 4%; but in the forest area only 9 cases in 5,531 inhabitants (0.2%). This geographical distribution as well as the temporal distribution coincide with frequent short-soaking of cassava roots (only one night) induced by an agro-ecological crisis. High levels of blood cyanide, mean 13.3 mumol/l (range: 0.1-76.3) and serum thiocyanate, mean (+/- SD) 401 (+/- 126) mumol/l, in a sample of 18 subjects from the savanna area confirm high cyanide exposure in this population with high prevalence of konzo. Prevention of konzo in Zaire is possible by promotion of sufficient soaking of cassava with strict adherence to traditional three nights soaking and the use of completely dry flour.

Adolescent↗