Monday, 28 November 2011

Whole brain atlas

Level 1: additional teaching resource

The whole brain atlas website, from Harvard, is a very useful resource to help you with your neuroanatomy and as a neuroradiology primer. Please refer to this site regularly. 

Evolutionary Neuroscience

Level 1: Evolutionary neurology / neuroscience

Please check-out this site: "Evolution; this view of life"

Saturday, 26 November 2011

Exercise: a possible treatment for neurodegeneration

Level 3

Spinocerebellar ataxia type 1 (SCA1) is caused by expansion of a translated CAG repeat in Ataxin-1 (ATXN1). To determine the long-term effects of exercise, this study implemented a mild exercise regimen in a mouse model of SCA1 and found a considerable improvement in survival accompanied by up-regulation of epidermal growth factor and consequential down-regulation of Capicua, which is an ATXN1 interactor. 

Conclusion: Thus, exercise might have long-term beneficial effects in other ataxias and neurodegenerative diseases.

See commentary: Gitler. Neuroscience. Another reason to exercise. Science. 2011 Nov 4;334(6056):606-7.

"The scientific case for regular aerobic exercise is compelling. Would you not agree?"

"If any of you are having problems motivating yourselves, I would suggest reading the book 'BORN TO RUN' by Christopher McDougall; you will be out running the moment you have read the book!"

Monday, 21 November 2011

Vertigo & Nystagmus with MRI

Level 3

Roberts et al. MRI magnetic field stimulates rotational sensors of the brain. Curr Biol. 2011 Oct 11;21(19):1635-40. 

Have you ever thought why patients and people get vertigo in and around MRI machines? 

Several mechanisms have been suggested to explain these sensations, yet without direct, objective measures, the cause has remained unknown, until now. 

This study has found that healthy human subjects developed a robust nystagmus while simply lying in the static magnetic field of an MRI machine. In comparison patients lacking labyrinthine function did not. 

They used the pattern of eye movements as a measure of vestibular stimulation to show that the stimulation is static (continuous, proportional to static magnetic field strength, requiring neither head movement nor dynamic change in magnetic field strength) and directional (sensitive to magnetic field polarity and head orientation). Their calculations and geometric model suggest that magnetic vestibular stimulation (MVS) derives from a Lorentz force resulting from interaction between the magnetic field and naturally occurring ionic currents in the labyrinthine endolymph fluid. This force pushes on the semicircular canal cupula, leading to nystagmus. 

They emphasize that the unique, dual role of endolymph in the delivery of both ionic current and fluid pressure, coupled with the cupula's function as a pressure sensor, makes magnetic-field-induced nystagmus and vertigo possible. 

Such effects could confound functional MRI studies of brain behavior, including resting-state brain activity.

Sunday, 20 November 2011

Babinski's sign

Level 1: The plantar or Babinski reflex is a elicited when the sole of the foot is stimulated with a blunt instrument. The reflex can take one of two forms. In normal adults the plantar reflex causes a flexor or downward response of the big toe. 

An upward response (extension) of the hallux is known as Babinski response or Babinski sign, after Joseph Babinski (1857–1932), a French neurologist of Polish origin. 

The presence of the Babinski sign is indicative of an upper motor neurone lesion. 

A Babinski sign is normal in infants and typically disappears when they start walking. 

The following YouTube clip shows you how to perform a plantar response:

Please use the back of neurotip or disposable orange stick (originally made from wood of the orange tree) to test the plantar response. The use of a tendon hammer or other non-disposable item (keys) are discouraged in the modern era as they are a potential source of hospital acquired infections. 

"In my personal experience the plantar response is not a very good sign; i.e. when there are obvious upper motor neurone signs it tends to be positive and when the plantar response is equivocal the other supporting signs (tone, power and tendon reflexes) are also equivocal."

"I was once told that 'you haven't completed your training as a neurologist unless you can make the plantar response go up or down'; this sums up the clinical utility of the sign."

"In my experience a strikingly postive or exaggerated Babinski response is typically associated with demyelinating disease. However, many other upper motor neurone lesions can cause an exaggerated response."

"Babinski actually described extension of the toe whilst walking barefoot as being the sign; I am not sure of the modern derivation."

Level 3+: There are a lot of other signs that have been described that essentially mean the same as the Babinski reflex; the following is a partial list:
  1. Bing sign – multiple pinpricks on the dorsum of the foot
  2. Cornell sign – scratching along the inner side of the extensor hallucis longus tendon
  3. Chaddock sign – stroking the lateral malleolus
  4. Gorda sign – flexing and suddenly releasing the 4th toe
  5. Gordon sign – squeezing the calf muscle
  6. Moniz sign – forceful passive plantar flexion of the ankle
  7. Oppenheim sign – applying pressure to the medial side of the tibia
  8. Schaeffer sign – squeezing the Achilles tendon
  9. Stransky sign – vigorously abducting and suddenly releasing the little toe
  10. Strümpell sign – patient attempts to flex the knee against resistance
  11. Throckmorton reflex – percussion over the metatarsophalangeal joint of the big toe
For those of you interested in the history of neurology will find the following article of interest: Joseph Babinski.

Saturday, 19 November 2011

Amateur neuroscientists

For those of you wanting to get hands on experience as experimental neuroscientists may find this site and set of experiments useful: 

Level 1: What neurological diseases are affected by changes in body temperature?

"Having in depth neuroscience knowledge enriches your clinical experience; try it!"

Saturday, 12 November 2011

Treating nystagmus

Level 3: as a follow-up to the previous posting re nystagmus

Epub ahead of printThurtell MJ, Leigh RJ. Treatment of Nystagmus. Curr Treat Options Neurol. 2011 Nov 10. 

Patients with congenital and acquired forms of nystagmus are commonly encountered in clinical practice. Many report visual symptoms, such as oscillopsia and blurred vision, which can be alleviated if the nystagmus can be suppressed.

Pharmacologic, optical, and surgical treatments are available, with the choice of treatment depending on the characteristics of the nystagmus and the severity of the associated visual symptoms. 
  1. Downbeat nystagmus can be treated with 4-aminopyridine, 3,4-diaminopyridine, or clonazepam
  2. Upbeat nystagmus can be reduced with memantine, 4-aminopyridine, or baclofen
  3. Torsional nystagmus may respond to gabapentin
  4. Acquired pendular nystagmus in patients with multiple sclerosis is often partially suppressed by gabapentin or memantine
  5. Acquired pendular nystagmus in patients with oculopalatal tremor can respond to gabapentin, memantine, or trihexyphenidyl
  6. Although acquired periodic alternating nystagmus is often completely suppressed by baclofen, memantine can be effective in refractory cases. 
  7. Seesaw nystagmus can be reduced with alcohol, clonazepam, or memantine
  8. Infantile nystagmus may not cause significant visual symptoms if "foveation periods" are well developed, but the nystagmus can be treated in symptomatic patients with gabapentin, memantine, acetazolamide, topical brinzolamide, contact lenses, or base-out prisms to induce convergence.
  9. Several surgical therapies have also been reported to improve infantile nystagmus syndrome (INS), but selection of the appropriate therapy requires preoperative evaluation of visual acuity and nystagmus intensity in different gaze positions. 
  10. Other treatment options for nystagmus include botulinum toxin injections into the extraocular muscles or retrobulbar space. 
  11. Electro-optical devices are currently being developed, in order to noninvasively negate the visual consequences of nystagmus.
"This paper makes it seems that nystagmus responds well to pharmacological therapies. In my experience this is not the case; the response is usual moderate and most of the drugs come with side effects that prevent higher doses."

Tuesday, 8 November 2011

Nerves in the superior orbital fissure

Level 2:

1. Lacrimal nerve (Vi)
2. Frontal nerve (Vi)
       Superior ophthalmic veins
3. Trochlear nerve (IV)
4. Superior division of oculomotor nerve (IIIs)
5. Nasociliary nerve (Vi)
6. Inferior division of oculomotor nerve (IIIi) + parasympathetic fibres
7. Abducens nerve (VI) + sympathetic fibres
       Inferior ophthalmic veins
"A blast from my past!  Does anyone recall the dirty mnemonic that helps you remember the structures that pass through the superior orbital fissure? If you do please share with us."

"I will post a case study in the next few days that will illustrate why you should try and remember the anatomy of this structure."

Extra reading: superior orbital fissure

Sunday, 6 November 2011

The philosophy of a blog

A blog is a two-way street; if you don't make comments and enter into a dialogue with the blogger and other readers it will be less valuable or at worst it will die. 

Please feel free to ask as many questions as you want and please make suggestions; requests are welcome.

I am new to using a blog as a teaching forum so any feedback would be very helpful. Do you want more, or less posts? Are the post too superficial or too detailed? Do you like the idea of three levels? etc.

Case study: 6th nerve palsy and ptosis

A 67-year old lady presented to the accident and emergency department with horizontal double-vision on looking to the left. When examined she was found to have a left sixth nerve palsy and mild ptosis of the left eye. When she was examined by the neurologist they confirmed the 6th nerve palsy and felt she also had features of a Horner's syndrome.

Level 1

What are the clinical features of a Horner's syndrome?
Where is the lesion?

Level 2

What is the most likely diagnosis?

Level 3

Describe the sympathetic innervation of the orbit and eye?
Is the Horner's syndrome pre or post ganglionic and what pharmacological tests can be done to localise the lesion?


Recommended revision: How to examine eye movements (including the use of the alternate cover test) and the pupils and the neuroanatomy of the cavernous sinus, superior orbital fissure and sympathetic and parasympathetic innervation of the orbit.

Thursday, 3 November 2011

Hoover's sign

Level 1:

Hoover’s sign of leg paresis is one of two signs named after Charles Franklin Hoover (1865–1927), an American physician, born in Cleveland, Ohio, who studied medicine at Harvard.

The manoeuvre is aimed to separate organic or non-functional from non-organic or functional paresis of the leg. The sign relies on the principle of synergistic contraction of muscle groups. Involuntary extension of the "paralysed" leg occurs when flexing the contralateral leg against resistance. 

The figure below explains the principles of the test. If the patient has weakness when you test extension of the right leg (A) but has detectable power in the right leg when you test flexion of the left leg (B) it implies that the patient is likely suffering from non-organic limb weakness (positive Hoover's sign). In B the extension of the right leg occurs due to involuntary contraction of synergistic muscles. 

I find a positive Hoover's sign a very useful clinical test to confirm a clinical suspicion of non-organic or medically unexplained symptoms. Please remember that a large number of patients may still have a organic disease despite a positive Hoover's sign; patients often try to enhance, or exaggerate, their symptoms and signs to make you take their complaints seriously; the medical jargon for this is "functional overlay". The diagnosis of medically unexplained symptoms is often very difficult; please don't rush to make this diagnosis particularly if you have any doubts. 

For those of you doing general medicine a positive Hoover’s sign may refer to inward movement of the lower rib cage during inspiration, implying a flat, but functioning, diaphragm. This is typically associated with hyperexpansion of the lungs due to air trapping, particularly emphysema. The flattened diaphragm contracts inwards instead of downwards, thereby paradoxically pulling the inferior ribs inwards with its movement.

Tuesday, 1 November 2011

Case study: diplopia and the alternate eye cover test

Apologies for not posting last week; I was away.

A 32 year old woman with relapsing-remitting multiple sclerosis (MS) presents with a 2 week history of horizontal double vision on looking to the right; the images were overlapping with the blurred or false image to the right.

Level 1

What and where is the lesion?

What is the alternate eye cover test?

What other clinical sign could this patient have and why?