Neurological Pathways Flashcards
What approach should you take in the diagnosis of a neurological lesion?
- The clue is often in the history. A neurological examination is done to confirm or rule out these impressions and clarify uncertainties.
- Ask yourself 3 questions:
- Where is the lesion located?
- Localising symptoms or signs present?
- Functional anatomy, including blood supply.
- What type of lesion?
- Speed of onset of symptoms.
- The natural history of the lesion (disease process); progressive, regressive, remitting-relapsing.
- A lesion restricted to the nervous system / part of a systemic illness (more than one system involved).
- What is the treatment?
- Where is the lesion located?
What would be found on observation and palpation in the event of an upper motor neuron lesion?
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Observation:
- No wasting or fasciculations.
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Palpation:
- Increased tone (maybe clonus)
- Weakness (pyramidal pattern)
- Increased reflexes
- Maybe extensor plantar
What would be found on observation and palpation in the event of an lower motor neuron lesion?
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Observation
- Wasting (atrophy)
- Maybe fasciculations
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Palpation
- Normal or reduced tone
- Weaknessdepends on where the lesion is
- Reduced or absent reflexes
Describe the pattern of weakness resulting from an upper motor neuron lesion.
- Arm extensors weaker than flexors (flexors are stronger).
- Leg flexors weaker than extensors (extensors are stronger).
- Some common presentations:
- Wasting of the first dorsal interossei
- Wasting of the tibialis anterior with the obvious spine of the tibia.
- Thenar eminence wasting (probably from a median nerve lesion).
- Weakness of gastrocnemius and soleus (weakness of the calf).

Describe the corticospinal tract.
- 90% of fibres follow the lateral corticospinal path (decussation).
- These pathways feed control to the distal muscles contralaterally.
- 10% follow the anterior (medial) corticospinal path (no decussation).
- These pathways feed control to the axial muscles bilaterally.

What is this picture showing?
What is the most common cause of this?

- Wrist drop on the right.
- Radial nerve palsy is the most common cause of this.
What is the most common problem of the median nerve problem (at the thumb)?
Carpal tunnel syndrome.
What is the most common ulnar nerve problem?
Ulnar nerve compression at the elbow.
What is the commonest nerve root to be affected in a lumbar disc problem?
How can you test this nerve?
- L5
- If patient has back pain and sciatica then you test big toe extension.
What are the reflexes which can be tested in the arm and the leg?
- C5/6 biceps and supinator
- C7 triceps
- Knee jerk - L3/4
- Ankle jerk - S1
- There is not a reflex for L5 (that’s why big toe extension is useful to check L5).
What happens to the nerve at the fibular head?
- Common peroneal nerve
- Compression of this nerve causes foot drop.
- Causes of foot drop can be an L4/5 lesion or the compression of the fibular head.

In which dermatome does the nipple lie?
And the umbilicus?
- Nipple = T4
- Umbilicus = T10
Where is C7 dermatome?
🖕
In which dermatome do the sole of the foot and the back of the calf lie?
S1
Describe the dorsal column medial leminiscal pathway.

What are the conditions which may affect the dorsal spinal column?
- Vitamin B12 deficiency (SCDC).
- HIV myelopathy
- Tabes dorsalis (syphilis)
- Multiple sclerosis
What is a syrinx?
- Syrinx - central cord lesion so it affects the crossing fibres in the spinothalamic area so in the neck it will be supplying the arms. The fibres from the lower part of the body have already crossed, so the lesion will not affect these areas, only the shoulders and hands.

What are the causes of central cord lesions?
- Syringomyelia
- MS
- Tumours
- Other
Describe the characteristics of a vascular brainstem lesion.
- Most likely to be an older male patient.
- Sudden onset (minutes).
- Most likely with vascular risk factors present.
Describe the characteristics of an infectious brainstem lesion.
- Onset of symptoms could be acute (hours) or subacute (days).
- Systemic inflammatory features present, e.g. fever.
Describe the characteristics of an autoimmune brainstem lesion.
- Most likely to be in a young female patient.
- Possibly relapsing-remitting course (e.g. MS).
- Maybe part of a systemic illness (vasculitis).
Describe the characteristics of tumour in the brainstem.
- Slow growing.
- Gradual.
- Weeks-years.
- Primary or metastasis.
Describe the characteristics of a degenerative brainstem lesion.
- Slow, onset over months to years, e.g. Parkinson’s Disease or motor neuron disease.
What are the signs which point to a lesion in the brainstem?
- If a motor tract is involved - contralateral hemiparesis (UMN signs).
- If ascending tracts (sensory) involved - contraleteral loss of fine touch and JPS or loss of pain and temperature in arms and legs.
- Ipsilateral ataxia in the limbs.
- Ipsilateral cranial nerve signs (LMN) in the head and neck.
- Ipsilateral Horner’s syndrome.
- Other non-cranial nerve nuclei may be involved if lesion within brainstem (rather than external compression).







