Review

Previous surgical procedures devised for intractable pain are the excision of painful area of the skin, peripheral neurotomy, intraspinal or intracranial posterior rhizotomies, anterolateral spinal cordotomy, spinothalamic tractotomy at medulla and mesencephalon for the pain of organic origin, and the prefrontal lobotomy for psychogenic pain. Unfortunately, these procedures are followed either by disturbance of physiologic sensory function or by changes of affect and personality. Partial gasserian gangliolysis successfully alleviated the trigeminal neuralgia without significant sensory disturbance of the face. Recent advances in stereotaxic technique has enabled us to attack the thalamus and other deep subcortical centers. This new method, together with recent neuroanatomico-physiological progress in regard to pain tract through intralaminar nuclear complex, resulted in discovery of thalamotomy destroying the nucleus centrum medianum with or without adjacent intralaminar nuclei, which eliminates the organic pain without any detectable sensory deficit. Anterior cingulectomy or cingulumotomy has developed to alleviate the psychogenic pain without psychological changes. These are the ideal pain-relieving procedures. A new method of percutaneous cervical cordotomy can be safely used for the debilitated patients with terminal malignant diseases

Spatial distribution of trace metals in benthic sediments of mangrove ecosystems of Niger Delta during wet and dry seasons.

<p>Spatial distribution of trace metals in benthic sediments of mangrove ecosystems of Niger Delta during wet and dry seasons.</p

The two principal components calculated by PCA reflecting the relationship of investigated trace metals and sedimentary variables.

<p>The two principal components calculated by PCA reflecting the relationship of investigated trace metals and sedimentary variables.</p

Hierarchical clustering analysis (Ward's Method) showing the relevant association among the parameters.

<p>Distance metrics are based on the Euclidean distance single linkage method (proximity matrix).</p

Trace metals concentrations (mg/kg) in sediment samples obtained for wet and dry seasons.

<p>Trace metals concentrations (mg/kg) in sediment samples obtained for wet and dry seasons.</p

Loadings of two principal components for benthic sedimentary variables.

<p>Loadings of two principal components for benthic sedimentary variables.</p

Map of study area showing the ecosystems in Niger Delta region of Nigeria (Inset: Map of Nigeria).

<p>Map of study area showing the ecosystems in Niger Delta region of Nigeria (Inset: Map of Nigeria).</p

Correlation matrix for trace metals, TOC, clay, sand and silt in benthic sediments.

<p>Correlation matrix for trace metals, TOC, clay, sand and silt in benthic sediments.</p

Relationships between trace metals in nonresidual/residual geochemical fractions and their corresponding individual contamination factors (ICFs) during the wet and dry seasons.

<p>The regression lines and equations in black color indicate metals in nonresidual fractions and ICFs; the regression lines and equations in red color represent metals in residual fractions and ICFs.</p

Sediment characterization variables in investigated ecosystems in Niger Delta.

<p>Sediment characterization variables in investigated ecosystems in Niger Delta.</p