Neurological Pathways

Question 1

What approach should you take in the diagnosis of a neurological lesion?

Answer 1

• 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:
  
  1. Where is the lesion located?
     
     • Localising symptoms or signs present?
     • Functional anatomy, including blood supply.
  2. 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).
  3. What is the treatment?

Question 2

What would be found on observation and palpation in the event of an upper motor neuron lesion?

Answer 2

• Observation:
  
  • ​No wasting or fasciculations.
• Palpation:
  
  • ​Increased tone (maybe clonus)
  • Weakness (pyramidal pattern)
  • Increased reflexes
  • Maybe extensor plantar

Question 3

What would be found on observation and palpation in the event of an lower motor neuron lesion?

Answer 3

• Observation
  
  • ​Wasting (atrophy)
  • Maybe fasciculations
• Palpation
  
  • ​Normal or reduced tone
  • Weaknessdepends on where the lesion is
  • Reduced or absent reflexes

Question 4

Describe the pattern of weakness resulting from an upper motor neuron lesion.

Answer 4

• 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).

Question 5

Describe the corticospinal tract.

Answer 5

• 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.

Question 6

What is this picture showing?

What is the most common cause of this?

Answer 6

• Wrist drop on the right.
• Radial nerve palsy is the most common cause of this.

Question 7

What is the most common problem of the median nerve problem (at the thumb)?

Answer 7

Carpal tunnel syndrome.

Question 8

What is the most common ulnar nerve problem?

Answer 8

Ulnar nerve compression at the elbow.

Question 9

What is the commonest nerve root to be affected in a lumbar disc problem?

How can you test this nerve?

Answer 9

• L5
• If patient has back pain and sciatica then you test big toe extension.

Question 10

What are the reflexes which can be tested in the arm and the leg?

Answer 10

• 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).

Question 11

What happens to the nerve at the fibular head?

Answer 11

• 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.

Question 12

In which dermatome does the nipple lie?

And the umbilicus?

Answer 12

• Nipple = T4
• Umbilicus = T10

Question 13

Where is C7 dermatome?

Answer 13

🖕

Question 14

In which dermatome do the sole of the foot and the back of the calf lie?

Answer 14

S1

Question 15

Describe the dorsal column medial leminiscal pathway.

Answer 15

Question 16

What are the conditions which may affect the dorsal spinal column?

Answer 16

• Vitamin B12 deficiency (SCDC).
• HIV myelopathy
• Tabes dorsalis (syphilis)
• Multiple sclerosis

Question 17

What is a syrinx?

Answer 17

• 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.

Question 18

What are the causes of central cord lesions?

Answer 18

• Syringomyelia
• MS
• Tumours
• Other

Question 19

Describe the characteristics of a vascular brainstem lesion.

Answer 19

• Most likely to be an older male patient.
• Sudden onset (minutes).
• Most likely with vascular risk factors present.

Question 20

Describe the characteristics of an infectious brainstem lesion.

Answer 20

• Onset of symptoms could be acute (hours) or subacute (days).
• Systemic inflammatory features present, e.g. fever.

Question 21

Describe the characteristics of an autoimmune brainstem lesion.

Answer 21

• Most likely to be in a young female patient.
• Possibly relapsing-remitting course (e.g. MS).
• Maybe part of a systemic illness (vasculitis).

Question 22

Describe the characteristics of tumour in the brainstem.

Answer 22

• Slow growing.
• Gradual.
• Weeks-years.
• Primary or metastasis.

Question 23

Describe the characteristics of a degenerative brainstem lesion.

Answer 23

• Slow, onset over months to years, e.g. Parkinson’s Disease or motor neuron disease.

Question 24

What are the signs which point to a lesion in the brainstem?

Answer 24

• 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).

Question 25

Waht are the midline structures in the brainstem? What are the clinical features of a lesion in each of these areas?

Answer 25

* **There are 4 structures in the brainstem beginning with M.** * From dorsal to ventral: * Motor nuclei and nerve * Lesion would cause ipsilateral features of CN lesion in the head and neck. * Medial longitudinal fasciculus * Lesion would cause ipsilateral inter-nuclear ophthalmoplegia. * Medial leminiscus * Lesion would cause contralateral loss of JPS. * Motor pathway (corticospinal and corticobulbar) * Lesion would cause contralateral UMN signs in the limbs and trunk.

Question 26

What are the UMN signs of a brainstem lesion?

Answer 26

* Spastic paresis / paralysis * Spasticity (tone) * Hyper-reflexia * Clonus (sustained, rhythmic contractions) * Positive Babinski's (up-going plantar reflex)

Question 27

Where do the groups of cranial nerves originate (in groups of 4)?

Answer 27

There are 4 cranial nerves in the medulla, 4 in the pons and 4 above the pons. This helps to locate a lesion in the brainstem.

Question 28

Which 4 motor nuceli are in the midline? What is caused by dysfunction of each of these?

Answer 28

* **Occulomotor nucleus (CNIII)** * **​**Dysfunction causes eye to turn out and down. * **Trochlear nucleus (CNIV)** * **​**Dysfunction causes inability to look down when the eye is looking inwards. * **Abducens nucleus (CNVI)** * **​**Dysfunction causes a problem abducting the eye. * **Hypoglossal nucleus (CNXII)** * **​**Dysfunction causes tongue to deviate towards the side of the lesion.

Question 29

Which cranial nerve nuclei lie laterally in the brainstem?

Answer 29

* **Vestibulocochlear (CNVIII) nucleus** * **​**Dysfunction causes ipsilateral deafness. * **Facial nucleus (CNVII) nucleus** * **​**Dysfunction causes ipsilateral facial weakness (superior and inferior facial muscles). * **Nucleus ambiguus: motor to the pharynx and larynx (CNIX and CNX)** * **​**Dysfunction causes ipsilateral palatal weakness (palate deviates away from the lesion). * If there is a problem with CNVII and CNVIII the lesion is likely to be in the pons. * If there is a problem with speech or swallowing the lesion is likely to be in the medulla.

Question 30

What are the structures on the **sides** of the **brainstem** which are likely to be affected by a vascular lesion?

Answer 30

* Structures on the sides of the brainstem including cranial nerves and their nuclei are likely to be affected by a vascular lesion at the different levels within the brainstem: * **S**pinocerebellar pathways * **S**pinothalamic pathway * **S**ensory nucleus of CNV (3 parts) * **S**ympathetic pathway

Question 31

A 45 year old male presents with a sudden onset of dysarthria. On examination he is found to have left hemiplegia; deviation of his tongue to the right and loss of JPS to the upper and lower left limbs. Where exactly is the lesion? What is the likely diagnosis?

Answer 31

Question 32

A 40 year old female is undergoing a yearly physical exam at her GP. Upon examination of her visual system, she is found to have impaired adduction in the left eye when asked to look to the right. There is also an apparent nystagmus in the right abducting eye. She is also found to have impaired adduction of the right eye when asked to look left. There is also an apparent nystagmus in the left abducting eye. On further questioning she tells her GP she had an episode of pain behind the right eye with partial loss of colour vision, which lasted 1 month in her 30s.

Answer 32

Question 33

A 60 year old male presents with sudden onset dysphagia and difficulty walking. He noticed his right eyelid had suddenly dropped. When he entered the room his gait seemed ataxic. On examination he has partial ptosis and meiosis of right eye, with loss of pain and temperature sensation on the same side of the face. In his left lower limbs he has lost sense of pain and temperature, however joint position sense remains intact. His palate has deviated to the left. Where is the lesion? What is the likely diagnosis?

Answer 33

Question 34

A 35 year old female presents with tinnitus and gradual loss of hearing in the right ear. The patient mentions she has also been having symptoms of vertigo over the past few weeks with occasional vomiting, in addition to slight weakness on the right side of her face. On examination she is found to have mild nystagmus, a right-sided facial paraesthesia and loss of corneal reflex. Where is the lesion? What is the likely diagnosis?

Answer 34

Question 35

18 year old man, brought in by ambulance to A&E with a stab wound. Right leg weakness, and loss of JPS in the right leg. Left leg spinothalamic loss to about T6.

Answer 35

* Classic presentation of Brown-Sequard syndrome. * Classically due to a stab wound in the back - it affects half of the spinal cord.

Question 36

What would cause the 'down and out' sign of the eye?

Answer 36

Every other muscle in the eye supplied by CN3, so if CN3 is damaged the eye is likely to be ‘down and out’ because the superior oblique moves the eye down, and the lateral rectus moves the eye out and that is all it can do.