Cranial fossae: Anterior, middle and posterior

How would you describe the location of this mass?Describe the location

a. Cerebellar

b. Infratentorial

c. Posterior fossa

d. Suboccipital

Answer: All of the above.

All these terms refer to the same space. The cerebellum resides in the posterior cranial fossa, in a location that is infratentorial or suboccipital.

Please note the “occipital” and “suboccipital” are NOT synonymous. (“Occipital” refers to the occipital lobe which is a part of the cerebrum and is supratentorial.)

The term “fossa” refers to a “scooped out” space, like the palm of your cupped hand. There are three fossa of the skull base: anterior, middle and posterior.

Cranial fossae

The anterior fossa (green) is where the frontal lobe is located.

The middle fossa (purple) is where the temporal lobe is located.

The posterior fossa (orange) is where the cerebellum is located.

The mass presented above is a tumor of the posterior fossa, that is, in an infratentorial location. It abuts the cerebellum. Surgical resection may be achieved through a suboccipital craniectomy.

Pituitary Adenoma

Pituitary Adenoma

Tumors at the pituitary are classified by SIZE and by SECRETIONS. They are treated with medication, surgery, or active surveillance.


A MICROadenoma is less than 1 cm and is often an incidental finding on an MRI of the brain done for other reasons, like workup of a headache. Unless it is secreting active hormone, a small adenoma is asymptomatic and will not cause visual disturbance or headache.

A MACROadenoma is larger than 1 cm and often presents with visual field cut due to compression of the optic chiasm. This produces tunnel vision, with a loss of peripheral vision called bitemporal hemianopsia.Pituitary macroadenoma. MRI T1 with contrast


Pituitary tumors are also classified by secretions.

A “non-functioning” adenoma does not secrete active hormone. It may actually suppress the production of normal hormones, with TSH, LH, and FSH being most vulnerable. Paradoxically it can result in *mild* elevation of PRL to about 20-100. It is often discovered by visual field loss caused by compression of the optic chiasm causing bitemporal hemianopsia.

Functioning” pituitary adenomas secrete active hormone. These tumors may secrete any hormone, but PRL, GH, and ACTH are by far the most common.

A PRL secreting tumor mimics the postpartum state in females, with amenorrhea and galactorrhea.  In males it’s even worse: impotence and poor libido! A prolactinoma can be quite large on initial presentation, and the serum PRL may measure in the several hundreds. Fortunately, these are nicely responsive to dopaminergic drugs like bromocriptine and cabergoline, shrinking the tumor dramatically within a few weeks.

A GH secreting tumor causes acromegaly in adults and giantism in children. Acromegaly in adults can occur insidiously, barely noticed by the patient and close family. On questioning the patient may admit enlarged hands and feet such that rings and shoes have been resized. Other stigmata include an enlarged brow, protruding jaw, or enlargement of the cartilaginous nose. One patient noticed that he could floss easier as his teeth separated due to elongation of the jaw! Surgery is needed to remove this tumor.

An ACTH secreting adenoma causes Cushing’s disease, named for Harvey Cushing, the father of neurosurgery. ACTH production in the pituitary stimulates production of cortisol in the adrenal gland. This produces clinical hallmarks of Cushing’s: moon face, buffalo hump, abdominal obesity with striae, wasting of arms and legs, and easy bruising. This, too, is a surgical condition.


Non-functioning MICROadenomas: No intervention needed, just periodic MRIs to check for growth, and periodic labs to check endocrine function.

Non-functioning MACROadenoma: Check endocrine labs, especially thyroid and sex hormones which can be diminished in the presence of a tumor. Check visual fields for bitemporal hemianopsia. Transphenoidal adenomectomy surgery can remarkably restore visual fields.

Prolactinoma: Pro-dopamine drugs like bromocriptine or cabergoline shrink the tumor dramatically and help with symptoms in males and females.

GH or ACTH secreting tumors usually need surgical resection to correct the harmful effects of these excess hormones.

Glioblastoma: Growth rate

Glioblastoma: How fast do they grow?

A 57 year old female presented with new onset seizure. An MRI was obtained showing a lesion in the right frontal/parietal region. You can see there is some mass effect, slight effacement of the ventricle, and a whiff of enhancement. Needle biopsy returned astrocytoma, WHO Grade 3.Astrocytoma WHO Grade 3

Surgical resection was recommended, but the patient chose instead to pursue external beam radiation and oral chemotherapy in the form of temozolomide.

Unfortunately, she now presents three months later with confusion, agitation, and left arm weakness. An MRI is again obtained. The tumor shows marked growth and different signal characteristics. You see that the mass is inhomogeneously enhancing, with marked mass effect, surrounding edema, ventricular effacement, and minimal midline shift.

Glioblastoma, WHO Grade 4

At this time the patient requests craniotomy for surgical debulking. The final pathologic diagnosis is Glioblastoma, WHO Grade 4.

This shows how rapidly a glioma can grow and transform to a higher grade, in this case just three months.

Brown-Sequard Syndrome: Hemisection of the Cord

Brown-Sequard syndromeBrown-Sequard Syndrome

Injury to half the spinal cord, or “hemisection of the cord,” can occur with trauma, tumor, or disc herniation. But most often it is seen in textbooks and in med school exams! The injury produces a unique constellation of findings: loss of motor and fine touch on the same side as the injury, and loss of pain/temperature on the opposite side. This is the Brown-Sequard syndrome.

Here’s how it happens.

First to orient you to the cartoons. We all know what this is.

The Brain, actually!

The brain, actually!

And now the brain with the brainstem and spinal cord.

Brain, brainstem, spinal cord

Of all the tracts in the spinal cord, there are really only three you need to know to get started. There is one efferent pathway, the corticospinal tract that carries motor signals from the brain to the body. There are two afferent pathways that carry sensory information to the brain, the dorsal columns which carry proprioception and fine touch, and the spinothalamic tract which transmits pain and temperature.

Note the location of the “crossover” of these tracts. This crossover point is the key to understanding the clinical features of the Brown-Sequard syndrome. The corticospinal tract and the dorsal columns cross over in the medulla, at the “decussation of pyramids.”

Corticospinal tract

Dorsal columns

By contrast, the spinothalamic tract doesn’t cross to the opposite side until it exits from the cord.

Spinothalamic tract

So what if you have an injury to the left side of the cord. What will be the expected clinical findings? What neuro deficits will result?

Left hemisection of the cord

This is the Brown-Sequard syndrome. Loss of motor and fine touch ipsilateral to the lesion, and contralateral loss of pain and temperature.Ipsilateral loss of motor and fine touch

Subdural Hematoma: When to Cut

Subdural Hematoma: When to Cut

Subdural hematoma is a common neurosurgical problem. A subdural usually occurs in patients with significant brain atrophy, such as the elderly or alcoholic. Even minor trauma can injure the bridging veins between the brain and the dura. Bleeding into the subdural space can occur rapidly, causing death in a matter of hours, or gradually over a period of weeks. The surgical management depends on whether the hemorrhage is acute or chronic.

Acute Subdural Hematoma

An acute subdural may result from trauma or in a patient on antiplatelet or anticoagulant drugs. Symptoms often include headache, hemiparesis or alteration of consciousness like agitation, lethargy, or coma. If the acute subdural is small, it can be managed non-surgically. Antiplatelet drugs are stopped, and coagulation is corrected. Careful clinical observation is imperative. The subdural may expand as it becomes chronic, as the osmotic effect of the blood products draws free CSF into the subdural space. All this to say, if a small, acute subdural isn’t surgical today, it may be in two weeks!

Here a moderate sized, acute subdural is seen. You will notice a hyperdense (white) mass over the cortical surface of the brain (arrow), with effacement of the gyral pattern adjacent to the subdural, along with asymmetry of the lateral ventricles and midline shift.

Acute subdural hematoma

This patient was taken to surgery for a craniotomy. In the craniotomy, a large section of the skull was removed. This is called “turning a flap.” It allows the evacuation of the blood clot. At surgery, the clot was so tenacious it could be picked up with forceps. This, by the way, is the reason that an acute subdural cannot be drained with a bur hole. The blood is congealed. It cannot be drained with a bur hole any more than a cup of Jello can be eaten with a straw: it is solid. Air is introduced into the head at the time of surgery. It appears jet black on CT (arrow).

Acute subdural hematoma post op

Chronic Subdural Hematoma

On CT, a chronic subdural is hypodense (dark). It represents old blood in a liquid state. How old is old? It takes about two weeks for an acute subdural to liquefy, and the CT appearance will evolve from hyperdense to hypodense as the hemorrhage becomes chronic. Symptoms include headache on the same side as the subdural. Hemiparesis may be mild or well compensated as weakness occurs gradually. Many patients experience hemiparesis as gait imbalance, or veering to one side. As the patient worsens, frank lethargy or coma may ensue.

Here is a chronic, subacute subdural hematoma. You see a hypodensity over the cerebral convexity anteriorly (double arrow), with a hyperdense component posteriorly (arrow). There is effacement of the gyral pattern, ventricular asymmetry and midline shift.

Subacute chronic subdural hematomaChronic subacute subdural hematoma with labels

This patient was taken to the operating room for bur-hole evacuation of the subdural. The liquefied blood was removed with a simple bur hole. Going back to the Jello analogy: If you leave Jello at room temperature, it turns to liquid; in this case you CAN drink it with a straw. Or drain a chronic subdural with a bur hole!

Here you can see postoperative air in the head (jet black, see arrow), with a mix of residual chronic and subacute blood, with improved mass effect. A drain is present (double arrow).

Chronic subdural hematoma post opChronic subdural hematoma post op with labels

To summarize, an acute subdural is a life threatening emergency, often requiring craniotomy within hours. The chronic subdural can be life threatening as well, but over a period of weeks, often treated with simple bur hole drainage.

On Call Pitfalls

On-Call Pitfalls

Things that Kill. Things that Bother.

Calls to the neurosurgery group can be divided into two groups: things that kill and things that bother. Listening for conditions that may become life threatening is a skill that comes with experience. What is “experience?” Paying attention to the things that have happened, often informed by mistakes you have made in the past!

Things that kill

MI. Specifically myocardial infarction in the post operative patient. Surgery is a stress to the body, and the patient with atherosclerotic coronary disease, for example, can be pushed over the edge simply from the physical impact of the surgical event. A cardiac event is suggested by any combination of chest pain, with radiation to the jaw or arm, with diaphoresis, with shortness of breath. Be quick to order a 12-lead EKG, cardiac enzymes, and pulse ox. If you wonder if the patient may be unstable, call the Rapid Response team for an immediate evaluation.

PE. Pulmonary embolism is characterized by chest pain around the ribs, diaphragm, or back, with shortness of breath, tachypnea, and anxiety about breathing, worse with lying, better sitting and leaning forward. Evaluate with pulse ox, ABG, chest x-ray, CT-Angiogram of the chest, and labs. Definitely call a Rapid Response whenever there is respiratory distress.

DVT. Here are the classic hallmarks of DVT: a painful, red, swollen, hot extremity. This is a little tricky to sort out on the neurosurgery service, since many of our patients have pain in an extremity to start with! So when you are called for pain in a leg or an arm, always ask: Is it swollen, red, and hot compared to the other? Order an ultrasound of that extremity to look for DVT, and unless you are sure it is not a DVT, remove the sequential compression device from the leg and keep the patient on bed rest. If a DVT is present, you’ll need to consider anticoagulation and the placement of an IVC filter.

CVA. Acute ischemic stroke presents with new-onset brain symptoms. Weakness or numbness on one side of the body, facial droop, slurred speech, confusion, and vertigo are all signs of a stroke. These symptoms are usually painless, and the patient almost always discounts their significance. Family members will often be the first to mention the changes. Any new onset stroke symptoms require an immediate CT of the head. Even in acute stroke, though, this is expected to be *normal* unless the stroke is hemorrhagic! Sometimes a follow up MRI is ordered with diffusion weighted images to prove the ischemic event. Other diagnostic steps include pulse ox, 12-lead EKG, labs including chemistry, CBC, lipid profile, and HbA1c. Risks and benefits of aspirin therapy can be weighed carefully in the post op neurosurgical patient.

Spinal cord compression and cauda equina syndrome. An epidural hematoma after a spinal procedure is a neurosurgical emergency. In the cervical spine this can follow anterior or posterior surgery. The hematoma compresses the cord causing severe local pain along with weakness, numbness, and spasticity in the extremities, with increased reflexes and sustained clonus. In the lumbar spine an epidural hematoma may compress the cauda equina causing severe local pain and numbness in the saddle region or in the legs, with weakness and depressed reflexes. Either case is a neurosurgical emergency and must be evaluated with immediate plain x-ray to visualize the bone structure and urgent MRI to image post op fluid collections, CSF, and the neural structures.

Drug allergy. A true drug allergy can be a life threatening emergency with anaphylaxis or hemodynamic shock. The lip swelling of angioedema or a macula-papular rash on the chest and trunk can herald an allergic reaction. Treatment begins with stopping the offending agent, a real trick since you usually don’t know which drug is the culprit! So you go with percentages: phenytoin and antibiotics are well known for causing allergic reactions. The next step of treatment is steroids and antihistamines to suppress the body’s allergic response. Above all, you must be mindful to protect the patient’s airway at all times.

Things that Bother

The vast majority of your calls will be for issues of comfort. I’m not minimizing these, but they occupy a different level of urgency. They are important in the patient’s recovery in that they can be obstacles to the patient’s physical progress. Here are the most common.

Pain. An inordinate amount of pain can signal an urgent problem like an epidural hematoma in the immediate post op patient, or infection days to weeks after surgery. After you have ruled out worrisome causes of pain, treat it using the standard drugs in your armamentarium: narcotics, muscle relaxants, anticonvulsants (like gabapentin), antidepressants (like amitriptyline), and sometimes a short course of steroids. Physical options include an ice pack to the surgical site. The PT/OT can instruct the patient in proper body mechanics to reduce pain with movement. The main idea is to control the pain well enough to allow physical progress in recovery.

Nausea. Pain can be nauseating, and the drugs used to treat pain can be nauseating! Nausea may reflect a post operative ileus that can occur after exposure for anterior lumbar surgery. Diagnostic evaluation with KUB can demonstrate an ileus. For the nauseated patient, limit the diet to ice chips or clear liquids until the gut is in better spirits.  Antiemetics and prokinetics are the medications most useful to keep on board, and in severe nausea these can be ordered around the clock for a period as a preventative. A physical technique to help prevent vomiting is slow, steady breathing. If vomiting is imminent, prevent aspiration by having the patient in a side-lying position or elevate the head of bed.

Constipation. There, I’ve said it! This is the number one complication of any hospitalized patient, and you will soon become an expert in preventing and treating constipation. Keep in mind that managing constipation in the *hospitalized* patient is different from the primary care setting. You’ll use docusate (Colace) in all hospitalized patients. Be quick to add polyethylene glycol (Miralax) and senna (Senokot) nightly for mild constipation. Bisacodyl functions like a stick of dynamite in the gut, and you’ll prefer the suppository route to “put the medicine right where it needs to work.” An enema is another option.

Itching. Itching can be an annoying but benign side effect of some medications like narcotics, or it may be a much more significant signal of an allergic reaction. For mild itching, a systemic antipruritic like diphenhydramine or hydroxyzine is useful. I avoid topical antihistamines and steroids because I don’t want my patient slathering medicine around a surgical incision. Blisters will appear with Stevens-Johnson syndrome, which is a life threatening emergency.

Call for help

As a neurosurgery beginner, you won’t have the experience, so learn from the experience of others. Keep your handbooks handy, both neurosurgery and medicine. Be quick to call your attending physician or a seasoned peer for advice. There are dangers and pitfalls lurking everywhere. As the saying goes: Learn from the mistakes of others—you won’t live long enough to make them all yourself.

When the Pain Is Worse than Films

When the Pain Is Worse than Films

Sometimes a patient will have excruciating pain, and rather bland films. Then your job is to make sense of the mismatch.

Secondary Gain

In some cases, “secondary gain” can motivate a patient to exaggerate their symptoms. The patient may receive compensatory pay for an injury that occurred while working. Maybe he or she gains sympathy from a significant other. I’ve seen cases where a passive spouse unconsciously employs a pain syndrome to get revenge on their abusive, controlling partner. The pain brings a benefit to the sufferer, and that benefit is the “secondary” gain.

However, secondary gain is always a diagnosis of exclusion. You may suspect it from the beginning, but in every case you are obligated to look for an underlying physiologic reason for the pain. Only after you have ruled out other causes of pain can you conclude the patient is seeking secondary gain.

Occult Fracture

She dove into water four feet deep, skinning her nose and chin. Stunned, she came back up to the surface complaining of terrible neck pain. Friends took her to the ER and this x-ray was obtained.

X-ray: Lateral C Spine

The plain X-ray looked normal

Her C spine was cleared and she was discharged. Over the next couple of days her neck pain persisted. Someone suggested chiropractic care, but first she sought the advice of a physician friend who recommended a CT scan. Here it is, showing a fracture of C7, with a traumatic subluxation of C7 on T1. Of great significance, the fracture was missed on the plain x-ray, which was technically perfect with visualization down to the C7-T1 disc.

CT C Spine Sagittal reconstruction


A 35 year old male with degenerative disc disease had been treated with some epidural steroid injections. Two injections gave partial relief for a couple of days, but within a month he worsened considerably. When we saw him, he was in severe pain, begging us for surgery. His MRI never looked that bad, and his worsening pain was curious to us. It didn’t all add up.Lumbar sagittal T1 without

So we sent him for another MRI without and with contrast, and blood work including CBC and Sed Rate. What was our suspicion? Infection or cancer. The pain was that bad. Sure enough, the MRI  showed enhancement about the L4-5 disc. It seems his run of the mill painful disc worsened due to an iatrogenic infection. Lumbar MRI T1 sagittal with contrastWe sent him for cultures and immediately started empiric antibiotics. He gradually improved over a full six weeks. No surgery was performed.

Spinal metastasis

If spine pain develops in someone with known, think spinal metastasis! The spinal pain of metastatic cancer is usually localized, without radicular or dermatomal radiation. It is worse at night while supine and better during the day. There may be dermatomal radiation if a spinal nerve is involved, or myelopathy if the cord is compressed. But usually the patient will complain of spine pain, worse at night. That alone is sufficient to warrant an MRI of the spine, without and with contrast, to evaluate spinal metastasis.MRI T spine without. Old T10 fracture

This 55 year old male had a T10 fracture a couple of years ago. He now presents with spine pain at night. MRI T spine is ordered, along with CT T spine. The cancers well known for metastasis to the spine are prostate, breast, and lung. Be on high alert in a patient with a history of cancer who now presents with new spinal pain.!MRI T spine. T1 with Contrast. Old fx T10. New cancer T12MRI T spine T1 with contrast. Old fx T10. New cancer T12CT axial shows invasion (lysis) of left T12 pedicle

The CT T spine confirms the lytic lesion of the left T12 pedicle, corresponding to the increased signal intensity on the MRI. The patient was sent for immediate radiation therapy for spinal metatstasis. He did not require surgery.

When pain exceeds imaging

When pain exceeds imaging, think FIRST –fracture–infection — cancer–as causes of spine pain. Check these out with MRI without and with contrast, CT, and even nuclear medicine bone scan. If, and only if, all these come back normal, then consider issues of malingering and secondary gain. But remember, your FIRST job is to find what others have missed or overlooked: occult fracture, infection, and cancer.