Transcript Dorsal Column * Medial Lemniscal System (DC-ML)

Dorsal Column – Medial
Lemniscal System (DC-ML)
Lec 5
Dorsal column-medial lemniscal
pathway
Romberg’s test
Sensory ataxia
Spinocerebellar tract (Fibers from arm)
Spinocerebellar tract (Fibers from leg)
Friedreich’s ataxia
1. Spino-cerebellar degeneration
2. Autosomal recessive disease
3. Symptoms begin before puberty; Ataxic gait,
dysarthria, loss of reflexes….
4. Most patients are wheelchair bound within
15-20 years of onset.
Spatial orientation of DC-ML system
• Lower part of the body is represented
medially
• Upper part of the body is represented lateraly
Types of sensations transmitted by DCML system
1. Proprioception (the sense of relative position
of parts of the body in space)
2. Precise touch,
3. Vibration sense,
4. Pressure sensation.
5. Two-point discrimination.
Tactile Hallucination;
Definition; feeling of tactile sensation without the presence of
an actual external stimuli.
Major causes of tactile hallucinations;
1. Cocaine, phencyclidine, Methamphetamine abuse.
2. Delirium tremens.
3. Phantom limb pain.
4. Dementia
5. Psychiatric disorders.
Tactile hallucination is subdivided to pleasant and unpleasant
tactile hallucinations.
Two-point discrimination
Somatosensory cortex
Damage to area 5 & 7 & / or Dorsal
column:
• Astereognosis
• Abarognosis
• Agraphesthesia
STEREOGNOSIS
GRAPHESTHESIA
Damage to SS Association area
Non-dominant hemisphere
(Brodmann’s area 5 & 7)
• Unilateral negligence
• Asomatognosia
The example is shown above and the patient's copy
to the right. Patients with left neglect sketch the
entire circle and write the numerals 12, 3, 6, and 9
at their correct locations. The patient was satisfied
that she had sketched the entire clock face shown
to her. She acknowledged her omissions when they
were indicated to her. Note the bunching of
numerals on the right side, another characteristic of
clock drawing by patients with neglect.
• Unilateral neglect when copying a scene, executed by the same patient.
Before she started copying, she was asked what she saw. She said, "A tree,
a house, and a fence." After she believed that she had copied the entire
picture, she was asked again what she saw in the original picture: "A tree
and a house." Note not only the absence of figures from the left side of
the scene, but also that only half the tree was drawn, thus demonstrating
two different kinds of neglect on drawing tasks (environment-based
neglect and object-based neglect). The distortion of elements in drawings
(constructional apraxia), as shown here, is also common in patients with
unilateral neglect
Trigeminal nucleus
Discriminative touch from face
The proprioceptive axons in the
trigeminal nerve